Methods and apparatus to detect air flow separation of an engine

ABSTRACT

Methods, apparatus, systems, and articles of manufacture are disclosed to detect air flow separation of an engine. An example apparatus includes hardware, and memory including instructions that, when executed, cause the hardware to at least determine an inlet flow separation parameter based on a first pressure value from a first pressure sensor included in a nacelle of a turbofan and a second pressure value from a second pressure sensor included in the nacelle, determine a severity level parameter based on the inlet flow separation parameter, the severity level parameter based on a difference between the first pressure value and the second pressure value, and adjust a contribution of airflow from aft of a fan of the turbofan based on the severity level parameter.

FIELD OF THE DISCLOSURE

This disclosure relates generally to a gas turbine engine and, moreparticularly, to methods and apparatus to detect air flow separation ofan engine.

BACKGROUND

A gas turbine engine generally includes, in serial flow order, an inletsection, a compressor section, a combustion section, a turbine section,and an exhaust section. In operation, air enters the inlet section andflows to the compressor section where one or more axial compressorsprogressively compress the air until it reaches the combustion section.Fuel mixes with the compressed air and burns within the combustionsection, thereby creating combustion gases. The combustion gases flowfrom the combustion section through a hot gas path defined within theturbine section and then exit the turbine section via the exhaustsection.

In particular configurations, the compressor section includes, in serialflow order, a low pressure compressor (“LP compressor”) and a highpressure compressor (“HP compressor”). The LP compressor and the HPcompressor may include one or more axially spaced apart stages. Eachstage may include a row of circumferentially spaced apart stator vanesand a row of circumferentially spaced apart rotor blades positioneddownstream of the row of stator vanes. The stator vanes direct the airflowing through the compressor section onto the rotor blades, whichimpart kinetic energy into the air to increase the pressure thereof.

Intakes of gas turbine engines are subject to cross winds and highincidence cross flows during takeoff, when in flight, etc., which canaffect the stability of air to the rotor blades. During such flightconditions, airflow at an inlet of the gas turbine engine can separateto cause inlet flow separation and reduce performance of the gas turbineengine.

SUMMARY

Methods and apparatus to control air flow separation of an engine aredisclosed herein.

An example apparatus disclosed herein includes hardware, and memoryincluding instructions that, when executed, cause the hardware to atleast determine an inlet flow separation parameter based on a firstpressure value from a first pressure sensor included in a nacelle of aturbofan and a second pressure value from a second pressure sensorincluded in the nacelle, determine a severity level parameter based onthe inlet flow separation parameter, the severity level parameter basedon a difference between the first pressure value and the second pressurevalue, and adjust a contribution of airflow from aft of a fan of theturbofan based on the severity level parameter.

Another example apparatus disclosed herein includes an inlet flowseparation parameter determiner to determine an inlet flow separationparameter based on a first pressure value from a first pressure sensorincluded in a nacelle of a turbofan and a second pressure value from asecond pressure sensor included in the nacelle, an inlet flow separationseverity level parameter determiner to determine a severity levelparameter based on the inlet flow separation parameter, the severitylevel parameter based on a difference between the first pressure valueand the second pressure value, and a command generator to adjust acontribution of airflow from aft of a fan of the turbofan based on theseverity level parameter.

An example non-transitory computer readable storage medium disclosedherein includes instructions that, when executed, cause at least oneprocessor to at least determine an inlet flow separation parameter basedon a first pressure value from a first pressure sensor included in anacelle of a turbofan and a second pressure value from a second pressuresensor included in the nacelle, determine a severity level parameterbased on the inlet flow separation parameter, the severity levelparameter based on a difference between the first pressure value and thesecond pressure value, and adjust a contribution of airflow from aft ofa fan of the turbofan based on the severity level parameter.

An example method disclosed herein includes determining an inlet flowseparation parameter based on a first pressure value from a firstpressure sensor included in a nacelle of a turbofan and a secondpressure value from a second pressure sensor included in the nacelle,determining a severity level parameter based on the inlet flowseparation parameter, the severity level parameter based on a differencebetween the first pressure value and the second pressure value, andadjusting a contribution of airflow from aft of a fan of the turbofanbased on the severity level parameter.

Yet another example apparatus disclosed herein includes hardware, andmemory including instructions that, when executed, cause the hardware toat least determine an inlet flow separation parameter based on a firstpressure value from a first pressure sensor included in a nacelle of aturbofan and a second pressure value from a second pressure sensorincluded in the nacelle, and determine a severity level parameter basedon the inlet flow separation parameter, the severity level parameterbased on a difference between the first pressure value and the secondpressure value.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of a first examplehigh-bypass turbofan-type gas turbine engine.

FIG. 2 is a schematic cross-sectional view of the first examplehigh-bypass turbofan-type gas turbine engine of FIG. 1 during an inletflow separation event.

FIG. 3 is a schematic cross-sectional view of a second examplehigh-bypass turbofan-type gas turbine engine including an examplecontroller monitoring inlet flow separation using example pressuresensors.

FIG. 4A is a schematic cross-sectional view of a third examplehigh-bypass turbofan-type gas turbine engine including the examplecontroller of FIG. 3 and example actuators to adjust contributions ofairflow to an inlet section of the third high-bypass turbofan-type gasturbine engine.

FIG. 4B is a schematic cross-sectional view of a fourth examplehigh-bypass turbofan-type gas turbine engine including the examplecontroller and example pressure sensors of FIG. 3 and example actuatorsto adjust contributions of airflow to an inlet section of the fourthhigh-bypass turbofan-type gas turbine engine.

FIG. 5 is a schematic cross-sectional view of the fourth examplehigh-bypass turbofan-type gas turbine engine of FIG. 4B during an inletflow separation event.

FIG. 6 is a block diagram of an implementation of the example controllerfor use with the high-bypass turbofan-type gas turbine engines of FIGS.3-5.

FIG. 7 is a table depicting example determinations used to detect inletflow separation for the high-bypass turbofan-type gas turbine engines ofFIGS. 3-5.

FIG. 8 is a flowchart representative of example machine readableinstructions that can be executed to implement the example controller ofFIGS. 3-6 to adjust an airflow contribution to an inlet of thehigh-bypass turbofan-type gas turbine engines of FIGS. 4A-5.

FIG. 9 is a flowchart representative of example machine readableinstructions that can be executed to implement the controller of FIGS.3-6 to determine inlet flow separation parameters based on sensor dataassociated with the high-bypass turbofan-type gas turbine engines ofFIGS. 3-5.

FIG. 10 is a flowchart representative of example machine readableinstructions that can be executed to implement the controller of FIGS.3-6 to detect inlet flow separation based on example inlet flowseparation parameters.

FIG. 11 is a flowchart representative of example machine readableinstructions that can be executed to implement the controller of FIGS.3-6 to identify example inlet flow separation control measure(s) basedon example inlet flow separation severity level parameters.

FIG. 12 is a flowchart representative of example machine readableinstructions that can be executed to implement the controller of FIGS.3-6 to adjust an airflow contribution to an inlet of the high-bypassturbofan-type gas turbine engines of FIGS. 4A, 4B, and/or 5.

FIG. 13 is a block diagram of an example processing platform structuredto execute the machine readable instructions of FIGS. 8-12 to implementthe controller of FIGS. 3-6.

The figures are not to scale. In general, the same reference numberswill be used throughout the drawing(s) and accompanying writtendescription to refer to the same or like parts.

DETAILED DESCRIPTION

Descriptors “first,” “second,” “third.” etc., are used herein whenidentifying multiple elements or components which may be referred toseparately. Unless otherwise specified or understood based on theircontext of use, such descriptors are not intended to impute any meaningof priority, physical order or arrangement in a list, or ordering intime but are merely used as labels for referring to multiple elements orcomponents separately for ease of understanding the disclosed examples.In some examples, the descriptor “first” may be used to refer to anelement in the detailed description, while the same element may bereferred to in a claim with a different descriptor such as “second” or“third.” In such instances, it should be understood that suchdescriptors are used merely for ease of referencing multiple elements orcomponents.

As used herein, the terms “upstream” and “downstream” refer to therelative direction with respect to fluid flow in a fluid pathway. Forexample, “upstream” refers to the direction from which the fluid flows,and “downstream” refers to the direction to which the fluid flows.

Performance of gas turbine engines used on aircraft (e.g., commercialaircraft) varies during different flight conditions experienced by theaircraft. In some instances, adverse flight conditions can reduce gasturbine engine performance. Such adverse flight conditions can includetakeoff of the aircraft or a cross-wind condition of the aircraft whenin flight. An inlet lip section located at the foremost end of thenacelle of the engine is typically designed to enable operation of theengine to prevent a separation of airflow from the inlet lip section ofthe nacelle during the adverse flight conditions. As used herein, theseparation of airflow from the inlet lip section of the nacelle isreferred to as “inlet flow separation” or “inlet airflow separation” andare used interchangeably. For example, the inlet lip section may requirea “thick” inlet lip section design to support operation of the engineduring specific flight conditions, such as cross-wind conditions,take-off, etc.

In some instances, inlet flow separation can cause significant asymmetryin the total pressure within the intake of the engine. In suchinstances, the asymmetrical total pressure can cause asymmetricalloading of fan blades of a fan of the engine, which can increasestresses of the fan blades. In some such instances, the stresses of thefan blades may result in reduced reliability and/or operating lifetimeof the fan blades and/or, more generally, the engine. Some severeinstances of inlet flow separation may cause compressor or engine surge,which is an increase in revolutions-per-minute (rpm) of a compressor ofthe engine. For instance, severe inlet flow separation may cause thecompressor and/or, more generally, the engine to stall.

Reference now will be made in detail to embodiments of the disclosure,one or more examples of which are illustrated in the drawings. Eachexample is provided by way of explanation of the disclosure, notlimitation of the disclosure. In fact, it will be apparent to thoseskilled in the art that various modifications and variations can be madein the present disclosure without departing from the scope or spirit ofthe disclosure. For instance, features illustrated or described as partof one example can be used with another example to yield a still furtherexample. Thus, it is intended that the present disclosure covers suchmodifications and variations as come within the scope of the appendedclaims and their equivalents.

Examples disclosed herein detect and control airflow separation of anengine, such as a gas turbine engine. In some disclosed examples, aninlet flow separation (IFS) controller determines one or more severitylevel parameters, or IFS severity level parameters, that can be used todetect IFS. For example, the IFS controller can determine a first IFSseverity level parameter based on an airflow direction, a second IFSseverity level parameter based on a pressure difference across inletsections of a nacelle of the engine, and/or a third IFS severity levelparameter based on an engine vibratory response. In such examples, theIFS controller can determine the first IFS severity level parameterand/or the second IFS severity level parameter based on air pressuredata from air pressure sensors included in an inlet lip section of thenacelle, an outlet lip section of the nacelle, etc. In some suchexamples, the IFS controller can determine the third IFS severity levelparameter based on acceleration data obtained from one or moreacceleration sensors monitoring one or more bearings (e.g., ballbearings, roller bearings, etc.) of the engine.

In some disclosed examples, the IFS controller can determine an IFSseverity level, or a degree or quantification of the IFS (if any), atthe inlet of the engine based on the IFS severity level parameter(s).For example, the IFS controller can determine a probability densityfunction based on the IFS severity level parameter(s). In such examples,the IFS controller can detect IFS at the inlet of the engine bycomparing the probability density function to one or more storedprobability density functions that can correspond to characterizationsor representations of the engine in diverse flight conditions.

In some disclosed examples, in response to detecting IFS, the IFScontroller can control one or more actuators included in the nacelle ofthe engine to reduce and/or otherwise eliminate the detected IFS. Forexample, the IFS controller can control an actuator to adjust (1) afirst airflow contribution from a first region aft of a fan of theengine and/or a second airflow contribution from a second region of acore of the engine to (2) a third region forward of the fan. In suchexamples, the IFS controller can reduce and/or otherwise eliminate theIFS by adjusting the airflow contribution of at least one of the firstregion or the second region. Advantageously, examples disclosed hereincan reduce and/or otherwise eliminate IFS and, thus, improve thereliability and operating lifetime of the engine by adjusting theairflow contributions from at least one of the first region or thesecond region to the third region.

Including” and “comprising” (and all forms and tenses thereof) are usedherein to be open ended terms. Thus, whenever a claim employs any formof “include” or “comprise” (e.g., comprises, includes, comprising,including, having, etc.) as a preamble or within a claim recitation ofany kind, it is to be understood that additional elements, terms, etc.,may be present without falling outside the scope of the correspondingclaim or recitation. As used herein, when the phrase “at least” is usedas the transition term in, for example, a preamble of a claim, it isopen-ended in the same manner as the term “comprising” and “including”are open ended. The term “and/or” when used, for example, in a form suchas A, B, and/or C refers to any combination or subset of A, B, C such as(1) A alone, (2) B alone, (3) C alone, (4) A with B, (5) A with C, (6) Bwith C, and (7) A with B and with C. As used herein in the context ofdescribing structures, components, items, objects and/or things, thephrase “at least one of A and B” is intended to refer to implementationsincluding any of (1) at least one A, (2) at least one B, and (3) atleast one A and at least one B. Similarly, as used herein in the contextof describing structures, components, items, objects and/or things, thephrase “at least one of A or B” is intended to refer to implementationsincluding any of (1) at least one A, (2) at least one B, and (3) atleast one A and at least one B. As used herein in the context ofdescribing the performance or execution of processes, instructions,actions, activities and/or steps, the phrase “at least one of A and B”is intended to refer to implementations including any of (1) at leastone A, (2) at least one B, and (3) at least one A and at least one B.Similarly, as used herein in the context of describing the performanceor execution of processes, instructions, actions, activities and/orsteps, the phrase “at least one of A or B” is intended to refer toimplementations including any of (1) at least one A, (2) at least one B.and (3) at least one A and at least one B.

As used herein, singular references (e.g., “a”, “an”, “first”, “second”,etc.) do not exclude a plurality. The term “a” or “an” entity, as usedherein, refers to one or more of that entity. The terms “a” (or “an”),“one or more”, and “at least one” can be used interchangeably herein.Furthermore, although individually listed, a plurality of means,elements or method actions may be implemented by, e.g., a single unit orprocessor. Additionally, although individual features may be included indifferent examples or claims, these may possibly be combined, and theinclusion in different examples or claims does not imply that acombination of features is not feasible and/or advantageous.

Referring now to the drawings, wherein identical numerals indicate thesame elements throughout the figures, FIG. 1 is a schematiccross-sectional view of a first example high-bypass turbofan-type gasturbine engine 100 (“turbofan 100”) as may incorporate various examplesdisclosed herein. As shown in FIG. 1, the first turbofan 100 defines alongitudinal or axial centerline axis 102 extending therethrough forreference. In general, the first turbofan 100 can include a core turbineor gas turbine engine 104 disposed downstream from a fan section 106.

The core turbine engine 104 can generally include a substantiallytubular outer casing 108 that defines an annular inlet 110. The outercasing 108 can be formed from a single casing or multiple casings. Theouter casing 108 encloses, in serial flow relationship, a compressorsection having a booster or low-pressure compressor 112 (“LP compressor112”) and a high-pressure compressor 114 (“HP compressor 114”), acombustion section 116, a turbine section having a high-pressure turbine118 (“HP turbine 118”) and a low-pressure turbine 120 (“LP turbine120”), and an exhaust section 122. A high-pressure shaft or spool 124(“HP shaft 124”) drivingly couples the HP turbine 118 and the HPcompressor 114. A low-pressure shaft or spool 126 (“LP shaft 126”)drivingly couples the LP turbine 120 and the LP compressor 112. The LPshaft 126 can also couple to a fan shaft or spool 128 of the fan section106. In some examples, the LP shaft 126 can couple directly to the fanshaft 128 (i.e., a direct-drive configuration). In alternativeconfigurations, the LP shaft 126 may couple to the fan shaft 128 via areduction gear 130 (i.e., an indirect-drive or geared-driveconfiguration).

As shown in FIG. 1, the fan section 106 includes a plurality of fanblades 132 (“fan” 132) coupled to and extending radially outwardly fromthe fan shaft 128. A first annular fan casing or first nacelle 134circumferentially encloses the fan section 106 and/or at least a portionof the core turbine 104. The first turbofan 100 includes a secondnacelle 135 opposite the first nacelle 134. The nacelles 134, 135 can besupported relative to the core turbine 104 by a plurality ofcircumferentially-spaced apart outlet guide vanes 136. Furthermore, adownstream section 138 of the nacelles 134, 135 can enclose an outerportion of the core turbine 104 to define a bypass airflow passage 140therebetween.

As illustrated in FIG. 1, air 142 enters an intake or inlet portion 144of the first turbofan 100 during operation thereof. A first portion 146of the air 142 flows into the bypass flow passage 140, while a secondportion 148 of the air 142 flows into the inlet 110 of the LP compressor112. One or more sequential stages of LP compressor stator vanes 150 andLP compressor rotor blades 152 coupled to the LP shaft 126 progressivelycompress the second portion 148 of the air 142 flowing through the LPcompressor 112 en route to the HP compressor 114. Next, one or moresequential stages of HP compressor stator vanes 154 and HP compressorrotor blades 156 coupled to the HP shaft 124 further compress the secondportion 148 of the air 142 flowing through the HP compressor 114. Thisprovides compressed air 158 to the combustion section 116 where it mixeswith fuel and burns to provide combustion gases 160.

The combustion gases 160 flow through the HP turbine 118 where one ormore sequential stages of HP turbine stator vanes 162 and HP turbinerotor blades 164 coupled to the HP shaft 124 extract a first portion ofkinetic and/or thermal energy therefrom. This energy extraction supportsoperation of the HP compressor 114. The combustion gases 160 then flowthrough the LP turbine 120 where one or more sequential stages of LPturbine stator vanes 166 and LP turbine rotor blades 168 coupled to theLP shaft 126 extract a second portion of thermal and/or kinetic energytherefrom. This energy extraction causes the LP shaft 126 to rotate,thereby supporting operation of the LP compressor 112 and/or rotation ofthe fan shaft 128. The combustion gases 160 then exit the core turbine104 through the exhaust section 122 thereof.

Along with the first turbofan 100, the core turbine 104 serves a similarpurpose and sees a similar environment in land-based gas turbines,turbojet engines in which the ratio of the first portion 146 of the air142 to the second portion 148 of the air 142 is less than that of aturbofan, and unducted fan engines in which the fan section 106 isdevoid of the nacelles 134, 135. In each of the turbofan, turbojet, andunducted engines, a speed reduction device (e.g., the reduction gearbox130) can be included between any shafts and spools. For example, thereduction gearbox 130 can be disposed between the LP shaft 126 and thefan shaft 128 of the fan section 106.

As depicted therein, the first turbofan 100 defines an axial directionA, a radial direction R, and a circumferential direction C. In general,the axial direction A extends generally parallel to the axial centerlineaxis 102, the radial direction R extends orthogonally outwardly from theaxial centerline axis 102, and the circumferential direction C extendsconcentrically around the axial centerline axis 102.

FIG. 2 is a schematic cross-sectional view of the first high-bypassturbofan-type gas turbine engine 100 of FIG. 1 during an inlet flowseparation (IFS) event. In FIG. 2, the IFS event is represented byexample arrows 202 moving towards a middle or mid-section of the fansection 106 of FIG. 1 and/or, more generally, towards the axialcenterline axis 102 of FIG. 1. For example, the arrows 202 can berepresentative of the air 142 separating at inlet sections (e.g.,nacelle inlet sections) 204, 206 of the nacelles 134, 135 of FIG. 1. Insuch examples, the IFS event can cause asymmetries in pressure (e.g.,air pressure) experience by the fan blades 132 of FIG. 1 and/orportion(s) of the fan section 106.

In FIG. 2, the IFS event can be caused by an example adverse flightcondition. For example, the first turbofan 100 can be coupled to anaircraft, and the IFS event can be caused in response to takeoff of theaircraft. In other examples, the first turbofan 100 can be coupled to anaircraft, and the IFD event can be caused in response to a cross-wind(e.g., a cross-wind condition, a cross-wind event, etc.) when theaircraft is in flight.

In FIG. 2, the nacelle inlet sections 204, 206 include a first nacelleinlet section 204 and a second nacelle inlet section 206. In FIG. 2, thefirst nacelle inlet section 204 has a first outer lip (e.g., a firstouter lip surface, a first outer lip section, etc.) 208 and a firstinner lip (e.g., a first inner lip surface, a first inner lip section,etc.) 210. In FIG. 2, the second nacelle inlet section 206 has a secondouter lip (e.g., a second outer lip surface, a second outer lip section,etc.) 212 and a second inner lip (e.g., a second inner lip surface, asecond inner lip section, etc.) 214.

In some examples, the fan blades 132 experience stresses (e.g.,mechanical stresses, vibration stresses, etc.) in response to the IFSevent. In response to the stresses, one(s) of the fan blades 132 canstructurally degrade, deteriorate, weaken, etc., over time and can causea reduction in reliability and/or operating lifetime of the fan blades132. For example, one(s) of the fan blades 132 can be damaged inresponse to the IFS event.

In some examples, the IFS event can cause significant asymmetries in thepressure at the inlet portion 144 of FIG. 1, which can cause compressoror engine surge. For example, at least one of the LP compressor 112 orthe HP compressor 114 can experience compressor surge in response to theIFS event. In such examples, the compressor surge can cause at least oneof the LP compressor 112 or the HP compressor 114 to stall and/or, moregenerally, can cause the core turbine 104 of FIGS. 1-2 to stall.

FIG. 3 is a schematic cross-sectional view of a second examplehigh-bypass turbofan-type gas turbine engine 300 including an examplecontroller (e.g., an IFS controller) 302 monitoring inlet flowseparation using example pressure sensors 304, 306, 308, 310. The secondturbofan 300 can be an example implementation of the first turbofan 100of FIGS. 1-2. For example, the second turbofan 300 can include all ofthe components of the first turbofan 100 of FIG. 1, such as the gasturbine engine 104, the tubular outer casing 108, the LP compressor 112,the HP compressor 114, etc., of FIGS. 1-2. In such examples, thedescription in connection with the first turbofan 100 of FIGS. 1-2 canbe applicable to the second turbofan 300 of FIG. 3.

In FIG. 3, the IFS controller 302 is a full-authority digital enginecontrol (FADEC) unit. Alternatively, the IFS controller 302 may be anengine control unit (ECU), an electronic engine control (EEC) unit,etc., or any other type of data acquisition and/or control computingdevice, processor platform (e.g., processor-based computing platform),etc. In FIG. 3, the IFS controller 302 is included in the second nacelle135. Alternatively, the IFS controller 302 may be included at any otherlocation of the second turbofan 300, such as the first nacelle 134.

In FIG. 3, the pressure sensors 304, 306, 308, 310 include a firstexample pressure sensor 304, a second example pressure sensor 306, athird example pressure sensor 308, and a fourth example pressure sensor310. In FIG. 3, the first pressure sensor 304 is coupled to the firstouter lip 208 of the first nacelle 134. In FIG. 3, the second pressuresensor 306 is coupled to the first inner lip 210 of the first nacelle134. The first pressure sensor 304 is configured to measure a first airpressure at the first outer lip 208. During an IFS event, such as theIFS event depicted in FIGS. 2-3, the first air pressure can approximatea stagnation pressure. The second pressure sensor 306 is configured tomeasure a second air pressure at the first inner lip 210. In FIG. 3, thesecond air pressure can approximate a static pressure.

In FIG. 3, the third pressure sensor 308 is coupled to the second outerlip 212 of the second nacelle 135. In FIG. 3, the fourth pressure sensor310 is coupled to the second inner lip 214 of the second nacelle 135.The third pressure sensor 308 is configured to measure a third airpressure at the second outer lip 212. During an IFS event, such as theIFS event depicted in FIGS. 2-3, the third air pressure can approximatea stagnation pressure. The fourth pressure sensor 310 is configured tomeasure a fourth air pressure at the second inner lip 214. In FIG. 3,the fourth air pressure can approximate a static pressure.

In FIG. 3, the first pressure sensor 304, the second pressure sensor306, the third pressure sensor 308, and the fourth pressure sensor 310are wireless sensors (e.g., wireless pressure sensors, wirelesspiezoelectric pressure sensors, wireless passive piezoelectric pressuresensors, etc.). For example, the first pressure sensor 304, the secondpressure sensor 306, the third pressure sensor 308, and the fourthpressure sensor 310 can be wireless passive piezoelectric pressuresensors. Alternatively, one or more of the first pressure sensor 304,the second pressure sensor 306, the third pressure sensor 308, and/orthe fourth pressure sensor 310 may be wired pressure sensors (e.g.,wired pressure sensors, wired piezoelectric pressure sensors, wiredpassive piezoelectric pressure sensors, etc.). Alternatively, one ormore of the first pressure sensor 304, the second pressure sensor 306,the third pressure sensor 308, and/or the fourth pressure sensor 310 maybe a different type of sensor, such as a diaphragm pressure sensor, apitot tube, etc.

In FIG. 3, the first pressure sensor 304 and the second pressure sensor306 are communicatively coupled to a first example antenna (e.g., anantenna module) 312. In FIG. 3, the third pressure sensor 308 and thefourth pressure sensor 310 are communicatively coupled to a secondexample antenna 314. In FIG. 3, the first antenna 312 is included in thefirst nacelle 134 and the second antenna 314 is included in the secondnacelle 135. Alternatively, both antennae 312, 314 may be included inthe first nacelle 134 while, in other examples, both antennae 312, 314can be included in the second nacelle 135.

In FIG. 3, the first antenna 312 and the second antenna 314 are coupled(e.g., communicatively coupled, electrically coupled, etc.) to the IFScontroller 302 via a wired connection (not shown). Alternatively, one orboth antennae 312, 314 may be coupled to the IFS controller 302 via awireless connection. In example operation, the first pressure sensor 304and the second pressure sensor 306 can transmit pressure data (e.g., airpressure data, air pressure measurements, etc.) to the IFS controller302 via the first antenna 312. In example operation, the third pressuresensor 308 and the fourth pressure sensor 310 can transmit pressure data(e.g., air pressure data, air pressure measurements, etc.) to the IFScontroller 302 via the second antenna 314.

In FIG. 3, the turbofan 300 includes example acceleration sensors 316,318 in an example bearing section 320. In FIG. 3, the bearing section320 includes, corresponds to, and/or otherwise is representative ofexample bearings 317, 319 (e.g., ball bearings, roller bearings, etc.)to support the fan shaft 128. In FIG. 3, the acceleration sensors 316,318 are coupled to the bearing section 320 (e.g., coupled to the one ormore bearings 317, 319 included in the bearing section 320) to monitorand/or otherwise measure forces (e.g., acceleration forces, vibrationforces, etc.) experienced by the bearings.

In FIG. 3, the acceleration sensors 316, 318 include a first exampleacceleration sensor 316 and a second example acceleration sensor 318. InFIG. 3, the acceleration sensors 316, 318 are accelerometers. Forexample, one or more of the acceleration sensors 316, 318 can be avibration sensor (e.g., a vibration sensor that includes a piezoelectriccrystal element), a gyroscope sensor, or a velocity sensor. In FIG. 3,the first acceleration sensor 316 is coupled to a first side of the fanshaft 128. In FIG. 3, the first acceleration sensor 316 is coupled to afirst example bearing 317 of the bearings 317, 319 included in thebearing section 320. In FIG. 3, the second acceleration sensor 318 iscoupled to a second side of the fan shaft 128, where the second side ison the opposite side of the axial centerline axis 102. In FIG. 3, thesecond acceleration sensor 318 is coupled to a second example bearing319 of the bearings 317, 319 included in the bearing section 320.

FIG. 4A is a schematic cross-sectional view of a third examplehigh-bypass turbofan-type gas turbine engine 400 including the IFScontroller 302 and the antennae 312, 314 of FIG. 3. Alternatively, thethird turbofan 400 may not include one or both antennae 312, 314. Thethird turbofan 400 can be an example implementation of the firstturbofan 100 of FIGS. 1-2 or portion(s) thereof and/or the secondturbofan 300 of FIG. 3 or portion(s) thereof. For example, the thirdturbofan 400 can include one or more of the components of the firstturbofan 100 of FIGS. 1-2 and/or the second turbofan 300 of FIG. 3, suchas the gas turbine engine 104, the tubular outer casing 108, the LPcompressor 112, the HP compressor 114, etc., of FIGS. 1-3, the IFScontroller 302, the antennae 312, 314 of FIG. 3, etc., and/or acombination thereof. In such examples, the description in connectionwith the first turbofan 100 of FIGS. 1-2 and/or the description inconnection with the second turbofan 30) of FIG. 3 can be applicable tothe third turbofan 400 of FIG. 4A.

In FIG. 4A, the third turbofan 400 includes example actuators 402, 404to adjust contributions of airflow from at least one of a first examplesection (e.g., a first airflow section, a first airflow contributionsection, a first airflow portion, a first airflow region, a firstairflow zone, etc.) 406 or a second example section (e.g., a secondairflow section, a second airflow contribution section, a second airflowportion, a second airflow region, a second airflow zone, etc.) 408 to athird example section (e.g., a third airflow section, a third airflowcontribution section, a third airflow portion, a third airflow region, athird airflow zone, etc.) 410. In FIG. 4A, the actuators 402, 404include a first example actuator 402 included in the first nacelle 134and a second example actuator 404 included in the second nacelle 135.

In FIG. 4A, the first section 406 corresponds to an airflow sectionbetween the LP compressor 112 and the HP compressor 114 and can begenerally referred to herein as “the core.” In FIG. 4A, the secondsection 408 can correspond to an airflow section aft of the fan blades132 and forward the outlet guide vanes 136. In FIG. 4A, the thirdsection 410 can correspond to an airflow section forward the fan blades132. For example, the third section 410 can include, correspond to,and/or otherwise be representative of the fan section 106.

In FIG. 4A, the airflow sections 406, 408, 410 are fluidly coupledand/or otherwise connected via example conduits (e.g., airflow conduits,bleed passages, bleed passageways, etc.) 412, 414. For example, airflowfrom the first section 406 and/or the second airflow section 408 can bedirected, routed, etc., to the third airflow section 410 via theconduits 412, 414 The conduits 412, 414 include a first example conduit412 included in the first nacelle 134 and a second example conduit 414included in the second nacelle 135. In FIG. 4A, the conduits 412, 414are composed and/or otherwise constructed from the same material(s) asthe nacelles 134, 135. For example, the conduits 412, 414 can beconstructed from one or more composite materials, one or more metallicmaterials, etc., and/or a combination thereof.

In FIG. 4A, the first conduit 412 has a first opening (e.g., a firstconduit opening) 416, a second opening 418 (e.g., a second conduitopening), and a third opening (e.g., a third conduit opening) 420. Thefirst opening 416 of the first conduit 412 is a first inlet (e.g., afirst conduit inlet) coupled to the first section 406. The first opening416 of the first conduit 412 is configured to obtain airflow (e.g.,pressurized airflow) from the first section 406. The second opening 418of the first conduit 412 is a second inlet (e.g., a second conduitinlet) coupled to the second section 408. The second opening 418 of thefirst conduit 412 is configured to obtain airflow (e.g., ambientairflow, non-pressurized airflow, incoming airflow, etc.) from thesecond section 408. The third opening 420 of the first conduit 412 is anoutlet (e.g., a conduit outlet) coupled to the third section 410. Thethird opening 420 of the first conduit 412 is configured to expel and/orotherwise output airflow to the third section 410.

In FIG. 4A, the second conduit 414 has a first opening (e.g., a firstconduit opening) 422, a second opening 424 (e.g., a second conduitopening), and a third opening (e.g., a third conduit opening) 426. Thefirst opening 422 of the second conduit 414 is a first inlet (e.g., afirst conduit inlet) coupled to the first section 406. The first opening422 of the second conduit 414 is configured to obtain airflow from thefirst section 406. The second opening 424 of the second conduit 414 is asecond inlet (e.g., a second conduit inlet) coupled to the secondsection 408. The second opening 424 of the second conduit 414 isconfigured to obtain airflow from the second section 408. The thirdopening 426 of the second conduit 414 is an outlet (e.g., a conduitoutlet) coupled to the third section 410. The third opening 420 of thesecond conduit 414 is configured to expel and/or otherwise outputairflow to the third section 410.

In FIG. 4A, airflow (e.g., bleed airflow) from the conduits 412, 414 areexpelled, introduced, etc., into the third section 410 in a directionopposite a direction of the air 142 (e.g., the oncoming air 142 at theinlet portion 144). The bleed airflow introduced into the third section410 from the conduits 412, 414 force the air 142 to flow around thebleed airflow. Advantageously, the bleed airflow introduced to the thirdsection 410 simulates and/or otherwise performs as a “thick” nacelle lipto reduce and/or otherwise eliminate IFS at the inlet portion 144.

In FIG. 4A, the airflow from the conduits 412, 414 can be obtained fromthe first section 406 and/or the second section 408 and, thus, can bedelivered to the third section 410 at relatively high pressure. Theairflow from the conduits 412, 414 are introduced to the third section410 at an angle relative to the air 142. Alternatively, the airflow fromthe conduits 412, 414 may be introduced to the third section 410 at anyangle based on a design of the nacelles 134, 135 and/or, more generally,the third turbofan 400.

In FIG. 4A, the actuators 402, 404 are valves actuated and/or otherwisecontrolled by solenoids. Alternatively, the actuators 402, 404 may beany other type of actuator. The actuators 402, 404 are operative in atleast three positions including a first position, a second position, anda third position. The first position, the second position, and the thirdposition can correspond to an amount of opening of the actuator 402, 404to the different sections 406, 408, 410. For example, the actuators 402,404 in the first position can direct a high quantity of air from thefirst section 406 to the third section 410 and a low quantity of airfrom the second section 408 to the third section 410. In such examples,the first position can correspond to the actuators 402, 404 being 70%,80%, 90%, etc., open to the first section 406 and 30%, 20%, 10%, etc.,open to the second section 408.

In other examples, the actuators 402, 404 in the second position candirect a medium quantity of air from the first section 406 to the thirdsection 410 and a medium quantity of air from the second section 408 tothe third section 410. In such examples, the second position cancorrespond to the actuators 402, 404 being 45%, 50%, 55%, etc., open tothe first section 406 and 55%, 50%, 45%, etc., open to the secondsection 408.

In yet other examples, the actuators 402, 404 in the third position candirect a low quantity of air from the first section 406 to the thirdsection 410 and a high quantity of air from the second section 408 tothe third section 410. In such examples, the third position cancorrespond to the actuators 402, 404 being 10%, 20%, 30%, etc., open tothe first section 406 and 90%, 80%, 70%, etc., open to the secondsection 408. For example, the low quantity of air is less than themedium quantity of air, and the medium quantity of air is less than thehigh quantity of air.

In FIG. 4A, the first antenna 312 is coupled to the first actuator 402and the second antenna 314 is coupled to the second actuator 404 viawired connections. Alternatively, the first antenna 312 may be coupledto the first actuator 402 via a first wireless connection and/or thesecond antenna 314 may be coupled to the second actuator 404 via asecond wireless connection. For example, the IFS controller 302 of FIG.3 can transmit a wireless command, direction, instruction, etc., toone(s) of the antennae 312, 314 to control one(s) of the actuators 402,404 to change positions. By invoking the actuators 402, 404 to changepositions, airflow contributions from at least one of the first section406 or the second section 408 can be adjusted to the third section 410.Advantageously, by adjusting the airflow contributions to the firstsection 406, the IFS controller 302 can reduce and/or otherwiseeliminate IFS in response to an adverse flight condition of the thirdturbofan 400. Advantageously, the IFS controller 302 can reduce and/orotherwise eliminate IFS by delivering pressurized airflow (e.g., airflowfrom the first section 406), ambient airflow (e.g., airflow from thesecond section 408), etc., and/or a combination thereof, to the thirdsection 410. For example, in response to a first severity level ofdetected IFS, the IFS controller 302 can deliver a first portion ofambient air from the second section 408 to the third section 410. Insuch examples, in response to a second severity level of detected IFSgreater than the first severity level of detected IFS (e.g., the secondseverity level is representative of greater or more severe IFS than thatof the first severity level), the IFS controller 302 can deliver (1) asecond portion of ambient air from the second section 408 to the thirdsection 408 and/or (2) a third portion of pressurized air from the firstsection 406 to the third section 408. In some such examples, the secondportion of ambient air can be less than and/or otherwise different fromthe first portion of ambient air.

FIG. 4B is a schematic cross-sectional view of a fourth examplehigh-bypass turbofan-type gas turbine engine 430 including the IFScontroller 302 of FIGS. 3-4A, the pressure sensors 304, 306, 308, 310 ofFIG. 3, and the antennae 312, 314 of FIGS. 3-4A. The fourth turbofan 430can be an example implementation of the first turbofan 100 of FIGS. 1-2or portion(s) thereof, the second turbofan 300 of FIG. 3 or portion(s)thereof, and/or the third turbofan 400 of FIG. 4A or portion(s) thereof.For example, the fourth turbofan 430 can include one or more of thecomponents of the first turbofan 100 of FIGS. 1-2, the second turbofan300 of FIG. 3, and/or the third turbofan 400 of FIG. 4A, such as the gasturbine engine 104, the tubular outer casing 108, the LP compressor 112,the HP compressor 114, etc., of FIGS. 1-3, the IFS controller 302, thepressure sensors 304, 306, 308, 310, the antennae 312, 314 of FIG. 3,etc., and/or a combination thereof. In such examples, the description inconnection with the first turbofan 100 of FIGS. 1-2, the description inconnection with the second turbofan 300 of FIG. 3, and/or thedescription in connection with the third turbofan 400 of FIG. 4A can beapplicable to the fourth turbofan 430 of FIG. 4B.

In FIG. 4B, the IFS controller 302, the first pressure sensor 304, andthe second pressure sensor 306 are in communication with and/orotherwise communicatively coupled to the first antenna 312 via wirelessconnection(s). In FIG. 4B, the first actuator 402 is in communicationwith and/or otherwise communicatively coupled to the first antenna 312via wired connection(s). Alternatively, the first actuator 402 may be incommunication with and/or otherwise communicatively coupled to the firstantenna 312 via wireless connection(s).

In FIG. 4B, the IFS controller 302, the third pressure sensor 308, andthe fourth pressure sensor 310 are in communication with and/orotherwise communicatively coupled to the second antenna 314 via wirelessconnection(s). In FIG. 4B, the second actuator 404 is in communicationwith and/or otherwise communicatively coupled to the second antenna 314via wired connection(s). Alternatively, the second actuator 404 may bein communication with and/or otherwise communicatively coupled to thesecond antenna 314 via wireless connection(s).

In FIG. 4B, the fourth turbofan 430 includes the IFS controller 302 todetect IFS at the inlet portion 144 based on pressure measurements fromat least one of the first pressure sensor 304, the second pressuresensor 306, the third pressure sensor 308, or the fourth pressure sensor310. In FIG. 4B, the IFS controller 302 can obtain pressure measurementsfrom one(s) of the pressure sensors 304, 306, 308, 310 via respectiveone(s) of the antennae 312, 314. In FIG. 4B, the IFS controller 302 cancontrol one(s) of the actuators 402, 404 based on the IFS detection. Forexample, the IFS controller 302 can generate command(s) and transmit thecommand(s) to the first actuator 402 and/or the second actuator 404. Insuch examples, in response to obtaining the command(s), the firstactuator 402 can move from a first position to a second position, thesecond actuator 404 can move from a third position to a fourth position,etc. In some such examples, the movement(s) of the first actuator 402and/or the second actuator 404 can adjust airflow contribution(s) fromat least one of the first section 406 or the second section 408 to thethird section 410.

FIG. 5 is a schematic cross-sectional view of the fourth high-bypassturbofan-type gas turbine engine 430 of FIG. 4B during an inlet flowseparation event. In FIG. 5, two different airflows 502, 504 aredepicted including a first airflow 502 and a second airflow 504. Thefirst airflow 502 corresponds to separation of the air 142 incident tothe nacelle inlet sections 204, 206, which causes the air 142 to movetowards the axial centerline axis 102. The first airflow 502 can causecompressor or engine surge, an increased engine vibratory response,etc., and/or a combination thereof that can cause a reduction inreliability and/or operating lifetime of the fan blades 132 or any othercomponent of the third turbofan 400.

In FIG. 5, the second airflow 504 corresponds to an example whereseparation of the air 142 incident to the nacelle inlet sections 204,206 does not occur and/or otherwise is minimized. For example, thesecond airflow 504 can correspond to the IFS event represented by thearrows 202 of FIG. 2. In FIG. 5, the second airflow 504 flows along theinner lips 210, 214 of the third turbofan 400. For example, in responseto the IFS controller 302 detecting the first airflow 502 (e.g.,detecting an IFS event), the IFS controller 302 can control one(s) ofthe actuator(s) 402, 404 of FIGS. 4A and/or 4B to bleed airflow from atleast one of the first section 406 or the second section 408 to thethird section 410. Advantageously, the IFS controller 302 can adjust thefirst airflow 502 to the second airflow 504 in response to adjustingairflow contributions from at least one of the first section 406 or thesecond section 408 to the third section 410.

FIG. 6 is a block diagram of an implementation of the IFS controller 302of FIGS. 3-5. The IFS controller 302 is configured to detect and/orcontrol IFS at the inlet 144 of the turbofans 300, 400, 430 of FIGS.3-5. In response to the detection of the IFS, the IFS controller 302 isconfigured to control one(s) of the actuator(s) 402, 404 of FIGS. 4-5 tocontrol contributions of airflow from at least one of the core (e.g.,the first section 406 of FIGS. 4-5) or aft of the fan 132 (e.g., thesecond section 408 of FIGS. 4-5) to forward of the fan 132 to reduceand/or otherwise eliminate the IFS.

In FIG. 6, the implementation of the IFS controller 302 includes anexample communication interface 610, an example inlet flow separationparameter determiner 620, an example inlet flow separation severitylevel parameter determiner 630, an example inlet flow separationdetector 640, an example command generator 650, an example alertgenerator 660, and an example database 670. In FIG. 6, the database 670includes example flight data 672, example sensor data 674, example IFSparameter(s) 676, example IFS severity level parameter(s) 678, exampleIFS detection model(s) 680, and example IFS control measure(s) 682.

In the illustrated example of FIG. 6, the IFS controller 302 includesthe communication interface 610 to communicate with sensor(s) (e.g., thefirst pressure sensor 304, the second pressure sensor 306, the thirdpressure sensor 308, the fourth pressure sensor 310, the firstacceleration sensor 316, and/or the second acceleration sensor 318 ofFIGS. 3-5), an antenna (e.g., the first antenna 312 and/or the secondantenna 314 of FIGS. 3-5), actuator(s) (e.g., the first actuator 402and/or the second actuator 404 of FIGS. 4-5), and/or example computingsystem(s) 612. For example, the computing system(s) 612 can correspondto one or more processor-based platforms associated with an aircraft,one or more processor-based platforms associated with an aircraft orturbofan manufacturer, etc. In some examples, the communicationinterface 610 obtains data or information from one or more of thesensor(s) 304, 306, 308, 310, the antennae 312, 314, the actuator(s)402, 404, and/or the computing system(s) 612 via a wired connection, awireless connection, etc., and/or a combination thereof.

In some examples, the communication interface 610 obtains the flightdata 672 from a computing system (e.g., the computing system(s) 612)onboard an aircraft. For example, the communication interface 610 canobtain altitude data, speed data (e.g., airspeed data), etc., associatedwith the turbofans 300, 400, 430 of FIGS. 3-5 and/or, more generally,the aircraft to which the turbofans 300, 400, 430 are coupled. In suchexamples, the communication interface 610 can store the altitude data,the speed data, etc., in the database 670 as the flight data 672.

In some examples, the communication interface 610 obtains an IFS commandfrom the computing system(s) 612. For example, the communicationinterface 610 can obtain an IFS command from an aircraft coupled to thethird turbofan 400 of FIG. 4A, a pilot controlling the aircraft from acockpit of the aircraft, etc. In such examples, the IFS command can beto increase an airflow contribution from the first section 406 or thesecond section 408 to the third section 410. In other examples, the IFScommand can be to decrease an airflow contribution from the firstsection 406 or the second section 408 to the third section 410.

In some examples, the communication interface 610 transmits an alert,data, information, etc., to the computing system onboard the aircraft.For example, the communication interface 610 can transmit an alert to anaircraft control system to display the alert on a user interface of adisplay in a cockpit for presentation to a pilot. In such examples, thealert can include data, information, etc., as described below inconnection with the alert generator 660.

In some examples, the communication interface 610 obtains sensor datafrom one(s) of the sensors 304, 306, 308, 310 of FIGS. 3-5. For example,the communication interface 610 can obtain pressure data (e.g., airpressure data) from the first pressure sensor 304 and the secondpressure sensor 306 via the first antenna 312. In other examples, thecommunication interface 610 can obtain pressure data (e.g., air pressuredata) from the third pressure sensor 308 and the fourth pressure sensor310 via the second antenna 314.

In some examples, the communication interface 610 transmits a command, adirection, an instruction, etc., to one(s) of the actuators 402, 404.For example, the communication interface 610 can deliver a command via awired connection to the actuators 402, 404 to adjust from a firstposition to a second position. In other examples, the communicationinterface 610 can transmit a command to the first actuator 402 to adjustfrom a first position to a second position via the first antenna 312. Inyet other examples, the communication interface 610 can transmit acommand to the second actuator 404 to adjust from the first position tothe second position via the second antenna 314.

In FIG. 6, the IFS controller 302 includes the IFS parameter determiner620 to determine the IFS parameter(s) 676 based on sensor dataassociated with a turbofan and store the IFS parameter(s) 676 in thedatabase 670. The IFS parameter(s) 676 can correspond to processed datavalues used by the IFS controller 302 to detect an IFS event and/ordetermine a quantification or severity of the IFS event. For example,the IFS parameter determiner 620 can determine one or more IFSparameters 676 associated with the turbofans 300, 400, 430 of FIGS. 3-5including a first air pressure value at the first outer lip 208, asecond air pressure value at the first inner lip 210, a third airpressure value at the second outer lip 212, a fourth air pressure valueat the second inner lip 214, an air density, a Mach number, and/or abearing load.

In some examples, the IFS parameter determiner 620 determines the firstair pressure value based on first air pressure data from the firstpressure sensor 304 of FIGS. 3-5. The IFS parameter determiner 620 candetermine the second air pressure value based on second air pressuredata from the second pressure sensor 306 of FIGS. 3-5. The IFS parameterdeterminer 620 can determine the third air pressure value based on thirdair pressure data from the third pressure sensor 308 of FIGS. 3-5. TheIFS parameter determiner 620 can determine the fourth air pressure valuebased on fourth air pressure data from the fourth pressure sensor 310 ofFIGS. 3-5.

In some examples, the IFS parameter determiner 620 determines an airdensity based on the altitude data. For example, the IFS parameterdeterminer 620 can determine an air density of the air 142 of FIGS. 1-5by mapping an altitude of the turbofans 300, 400, 430, the aircraftcoupled to the turbofans 300, 400, 430, etc., stored in the flight data672 to the air density. In such examples, an altitude-to-air densitymapping can be stored in a look-up table (e.g., a look-up table in thedatabase 670).

In some examples, the IFS parameter determiner 620 determines a Machnumber based on the speed data. For example, the IFS parameterdeterminer 620 can obtain the speed data from the flight data 672 anddetermine the Mach number based on the obtained speed data.

In some examples, the IFS parameter determiner 620 determines a bearingload, a force value, a vibration response, etc., and/or a combinationthereof based on acceleration data. For example, the communicationinterface 610 can obtain acceleration data from one(s) of theacceleration sensors 316, 318 coupled to one(s) of the bearings 317, 319of the bearing section 320 of the engine 104 of FIGS. 3-5. The IFSparameter determiner 620 can determine a first bearing load, a firstforce value, a first vibration response, etc., associated with the firstbearing 317 based on first acceleration data obtained from the firstacceleration sensor 316. The IFS parameter determiner 620 can determinea second bearing load, a second force value, a second vibrationresponse, etc., associated with the second bearing 319 based on secondacceleration data obtained from the second acceleration sensor 318.

In FIG. 6, the IFS controller 302 includes the IFS severity levelparameter determiner 630 to determine severity level parameters, such asthe IFS severity level parameter(s) 678, based on the IFS parameter(s)676. The IFS severity level parameter determiner 630 can store the IFSseverity level parameter(s) 678 in the database 670. The IFS severitylevel parameter(s) 678 can correspond to processed data values used bythe IFS controller 302 to determine a quantification or severity of theIFS event. For example, the IFS severity level parameter determiner 630can determine one or more IFS severity level parameters 678 associatedwith the turbofans 300, 400, 430 of FIGS. 3-5 including a first exampleseverity level parameter 702 (FIG. 7) based on an air flow direction, asecond example severity level parameter 704 (FIG. 7) based on a pressuredifference outer nacelle pressure(s) and inner nacelle pressure(s),and/or a third example severity level parameter 706 (FIG. 7) based on anengine vibratory response.

Turning to FIG. 7, an example IFS severity level table 700 depictsexample determinations by the IFS controller 302 of FIGS. 3-6 used todetect IFS of the turbofans 300, 400, 430 of FIGS. 3-5. The IFS severitylevel table 700 is representative of example logic that can be used bythe IFS controller 302 to determine the first IFS severity levelparameter 702, the second IFS severity level parameter 704, and thethird IFS severity level parameter 706. Alternatively, the IFScontroller 302 may determine fewer or more severity level parametersthan depicted in FIG. 7.

In FIG. 7, the first IFS severity level parameter 702 is indicative of aflow direction (e.g., an adverse flow direction, an adverse airflowdirection, etc.). For example, the IFS severity level parameterdeterminer 630 of FIG. 6 can determine the flow direction based on adifference between Ps (e.g., a first pressure value from the firstpressure sensor 304, a second pressure value from the third pressuresensor 308, etc.) and Pt (e.g., a pressure threshold), where Pt can be apre-defined or pre-determined pressure value. In such examples, Pscorresponds to a pressure value at a nacelle outer lip, such as thefirst outer lip 208 (e.g., a pressure value or measurement from thefirst pressure sensor 304), the second outer lip 212 (e.g., a pressurevalue or measurement from the third pressure sensor 308), etc. Inresponse to determining that the difference satisfies a threshold, suchas the difference being less than 0 (e.g., Ps<Pt) or a different value,the IFS severity level parameter determiner 630 can determine that theflow direction is substantially parallel (e.g., parallel within a rangeof −5 to 5 degrees, −2 to 2 degrees, etc.) to the nacelle outer lip.

In some examples, the IFS severity level parameter determiner 630 candetermine that the turbofans 300, 400, 430 are experiencing a cross-windbased on the flow direction. For example, the IFS severity levelparameter determiner 630 can detect a cross wind based on the differencebeing approximately 0 (e.g., Ps=Pt, Ps is approximately equal to Pt,etc.), which can be indicative of the flow direction being normal (e.g.,90 degrees to the nacelle outer lip, normal within a range of 85 to 95degrees to the nacelle outer lip, etc.) and/or otherwise incident to thenacelle outer lip. In such examples, the IFS severity level parameterdeterminer 630 can determine that the airflow is stagnant, which can beindicative of a cross wind, based on the difference being approximately0.

In some examples, the second IFS severity level parameter 704 isindicative of a nacelle inlet pressure difference based on a differencebetween a first pressure value at an outer lip of a nacelle (Psouter)and a second pressure value at an inner lip of the nacelle (Psinner).For example, the IFS severity level parameter determiner 630 candetermine the second IFS severity level parameter 704 by determining adifference between a first pressure value at the first outer lip 208 ofthe first nacelle 134 and a second pressure value at the first inner lip210 of the first nacelle 134. In such examples, the IFS severity levelparameter determiner 630 can determine the second IFS severity levelparameter 704 by normalizing the difference to a Mach number (v) and airdensity (p) of ambient air as described below in Equation (1):

$\begin{matrix}{{{NACELLE}\mspace{14mu}{INLET}\mspace{14mu}{PRESSURE}\mspace{14mu}{DIFFERENCE}} = \frac{\left( {{Psouter} - {Psinner}} \right)}{\rho \times v^{2}}} & {{Equation}\mspace{14mu}(1)}\end{matrix}$

In some examples, the third IFS severity level parameter 706 isindicative of an engine vibratory response based on acceleration datafrom bearing accelerometers (e.g., the acceleration sensors 316, 318 ofFIGS. 3-5). For example, the IFS severity level parameter determiner 630can determine the third IFS severity level parameter 706 by generatingan acoustic or vibration response of a load at a bearing (e.g., thefirst bearing 317, the second bearing 319, etc.) included in the bearingsection 320 of the engine 104 of FIGS. 3-5 based on acceleration datafrom one(s) of the acceleration sensors 316, 318 coupled to thebearing(s) 317, 319.

In FIG. 7, the IFS severity level parameter determiner 630 can determinethe first IFS severity level parameter 702, the second IFS severitylevel parameter 704, and the third IFS severity level parameter 706based on example weight factors (e.g., scaling factors) 708, 710, 712.The weight factors 708 include a first example weight factor (wtFD) 708corresponding to a flow direction weight factor, a second example weightfactor (wtDP) 710 corresponding to a differential pressure weightfactor, and a third example weight factor (wtEVR) corresponding to anengine vibratory response weight factor. The IFS severity levelparameter determiner 630 can use the weight factors to increase ordecrease an effect, impact, and/or influence of the respective IFSseverity level parameters 702, 704, 706 on the detection of an IFS eventand/or a quantification of a severity of the detected IFS event.

In FIG. 7, the IFS severity level parameter determiner 630 can determinethe first IFS severity level parameter 702 based on a multiplicationand/or other mathematical operation of an output of thedefinition/determination logic for the flow direction and the firstweight factor 708. In FIG. 7, the IFS severity level parameterdeterminer 630 can determine the second IFS severity level parameter 704based on a multiplication and/or other mathematical operation of anoutput of the definition/determination logic for the nacelle inletpressure difference and the second weight factor 710. In FIG. 7, the IFSseverity level parameter determiner 630 can determine the third IFSseverity level parameter 706 based on a multiplication and/or othermathematical operation of an output of the definition/determinationlogic for the engine vibratory response and the third weight factor 712.

Turning back to FIG. 6, the IFS controller 302 includes the IFS detector640 to detect an IFS condition, event, etc., of the turbofans 300, 400,430 of FIGS. 3-5 based on the IFS parameter(s) 676. In some examples,the IFS detector 640 detects IFS based on a comparison of an IFSdetection model to one(s) of the IFS detection model(s) 680 stored inthe database 670. For example, the IFS detector 640 can generate an IFSdetection model based on a probability density function (PDF). The IFSdetector 640 can generate and/or otherwise determine the PDF based on atleast one of the first IFS severity level parameter 702, the second IFSseverity level parameter 704, or the third IFS severity level parameter706. Alternatively, the IFS detection model may be a machine-learningmodel, such as a neural network (e.g., a convolution neural network, adeep neural network, etc.).

Turning back to FIG. 7, the IFS detector 640 can generate an IFSdetection model including a PDF based on the first IFS severity levelparameter 702, the second IFS severity level parameter 704, or the thirdIFS severity level parameter 706. The IFS detector 640 can compare thePDF to a first example PDF 714, a second example PDF 716, and a thirdexample PDF 718. The PDFs 714, 716, 718 can be stored in the database670 as the IFS detection models 680. In FIG. 7, the first PDF 714 cancorrespond to a no IFS condition or a clean airflow condition at theinlet 144 of FIGS. 1-5.

In FIG. 7, the second PDF 716 can correspond to a PDF generated based onan adverse inlet flow direction and an impact on inlet airflow oncomingto the fan 132. The IFS detector 640 can determine the adverse inletflow direction based on the first IFS severity level parameter 702. TheIFS detector 640 can determine the impact on the inlet airflow oncomingto the fan 132 based on the second IFS severity level parameter 704. InFIG. 7, the adverse inlet flow direction and the impact on inlet airflowoncoming to the fan 132 can cause a mean shift to the first PDF 714 togenerate the second PDF 716.

In FIG. 7, the third PDF 718 can correspond to a PDF generated based onan adverse inlet flow direction, an impact on inlet airflow oncoming tothe fan 132, and an adverse engine vibration response. The IFS detector640 can determine the adverse engine vibration response based on thethird IFS severity level parameter 706. In FIG. 7, the adverse inletflow direction, the impact on inlet airflow oncoming to the fan 132, andthe adverse engine vibration response can cause a mean shift and astandard deviation (STD DEV) variation to the first PDF 714 to generatethe third PDF 718. In some examples, the IFS detector 640 detects IFS atthe inlet 144 of the turbofans 300, 400, 430 based on the comparison(s)of a PDF based on the IFS severity level parameters 702, 704, 706 andthe PDFs 714, 716, 718 of FIG. 7.

Turning back to FIG. 6, the IFS controller 302 includes the commandgenerator 650 to generate a command, a direction, an instruction, etc.,to control and/or otherwise invoke one(s) of the actuator(s) 402, 404 ofFIGS. 4-5. In some examples, the command generator 650 invokes thecommunication interface 610 to transmit a command to the first antenna312 to relay the command to the first actuator 402 to move the firstactuator 402 from a first position to a second position, where the firstposition is different from the second position. In some such examples,the command generator 650 can invoke the first actuator 402 tofacilitate a high airflow contribution from the first section 406 and alow airflow contribution from the second section 408 to the thirdsection 410.

In some examples, the command generator 650 invokes the communicationinterface 610 to transmit a command to the second actuator 404 via awired connection (e.g., without transmitting the command to the secondantenna 314). In such examples, the command generator 650 can invoke thesecond actuator 404 to adjust positions based on the command. In somesuch examples, the command generator 650 can invoke the second actuator404 to facilitate a low airflow contribution from the first section 406and a high airflow contribution from the second section 408 to the thirdsection 410. In other examples, the command generator 650 can invoke thesecond actuator 404 to facilitate a medium airflow contribution from thefirst section 406 and a medium airflow contribution from the secondsection 408 to the third section 410.

In some examples, the command generator 650 determines one(s) of the IFScontrol measure(s) 682 based on the IFS severity level parameter(s) 678.In FIG. 6, the IFS control measure(s) 682 are command(s),instruction(s), sequence(s) of command(s) or instruction(s), etc.,and/or a combination thereof that can be used by the command generator650 to reduce and/or otherwise eliminate IFS. For example, the commandgenerator 650 can determine not to deploy one of the IFS controlmeasure(s) 682 when the first IFS severity level parameter 702 indicatesthere is no IFS.

In some examples, the command generator 650 deploys a first one of theIFS control measure(s) 682 based on the IFS severity level parameter(s)678. For example, the command generator 650 can execute the first one ofthe IFS control measure(s) 682 by controlling the actuator(s) 402, 404to facilitate a high core airflow contribution (e.g., a highcontribution of airflow from the first section 406) and a low fanairflow contribution (e.g., a low contribution of airflow from thesecond section 408) when the first IFS severity level parameter 702and/or the second IFS severity level parameter 704 indicates there issubstantially high IFS at the inlet 144. In such examples, the first oneof the IFS control measure(s) 682 can include the command generator 650transmitting a first command to the first actuator 402, a second commandto the second actuator 404, a command sequence of transmitting thesecond command after the first command, etc.

In some examples, the command generator 650 deploys a second one of theIFS control measure(s) 682 based on the IFS severity level parameter(s)678. For example, the command generator 650 can execute the second oneof the IFS control measure(s) 682 by controlling the actuator(s) 402,404 to facilitate a medium core airflow contribution (e.g., a mediumcontribution of airflow from the first section 406) and a medium fanairflow contribution (e.g., a medium contribution of airflow from thesecond section 408) when the first IFS severity level parameter 702and/or the second IFS severity level parameter 704 indicates there is amedium quantification of IFS at the inlet 144. In such examples, thesecond one of the IFS control measure(s) 682 can include the commandgenerator 650 transmitting a first command to the first actuator 402, asecond command to the second actuator 404, a command sequence oftransmitting the second command after the first command, etc.

In some examples, the command generator 650 deploys a third one of theIFS control measure(s) 682 based on the IFS severity level parameter(s)678. For example, the command generator 650 can execute the third one ofthe IFS control measure(s) 682 by controlling the actuator(s) 402, 404to facilitate a low core airflow contribution (e.g., a low contributionof airflow from the first section 406) and a high fan airflowcontribution (e.g., a high contribution of airflow from the secondsection 408) when the first IFS severity level parameter 702 and/or thesecond IFS severity level parameter 704 indicates there is substantiallylow IFS at the inlet 144. In such examples, the third one of the IFScontrol measure(s) 682 can include the command generator 650transmitting a first command to the first actuator 402, a second commandto the second actuator 404, a command sequence of transmitting thesecond command after the first command, etc.

In FIG. 6, the IFS controller 302 includes the alert generator 660 togenerate an alert, alarm, a warning, etc., in response to detecting IFSat the inlet 144 of the turbofans 300, 400, 430 of FIGS. 3-5. In someexamples, the alert generator 660 generates an alert by generating a logand/or a report, transmitting the alert to be presented on one or moredisplays (e.g., one or more displays in a cockpit of an aircraft, on asmartphone, tablet, or laptop display, etc.), transmitting the alert toa network (e.g., an aircraft control network), etc., and/or acombination thereof.

In some examples, the alert generator 660 stores information (e.g., agenerated alert, a log, a report, etc.) in the database 670 and/orretrieves information (e.g., the IFS parameter(s) 676, the IFS severitylevel parameter(s) 678, etc.) from the database 670 to be included inthe alert. For example, the alert generator 660 can store a reportincluding a maintenance alert for the fan blades 132 in the database 670based on an engine vibratory response stored in the IFS severity levelparameter(s) 678.

In some examples, the alert generator 660 records and/or otherwisestores the flight data 672 (FIG. 6) and/or the sensor data 674 (FIG. 6)associated with time(s) before, during, and/or after actuation(s) of thefirst actuator 402 and/or the second actuator 404 in the database 670.In such examples, the alert generator 660 can record which one(s) of theactuators 402, 404 are invoked in response to IFS command(s),position(s) of one(s) of the actuators 402, 404, etc., and/or acombination thereof.

In FIG. 6, the IFS controller 302 includes the database 670 to recordand/or otherwise store data, such as the flight data 672, the sensordata 674, the IFS parameter(s) 676, the IFS severity level parameter(s)678, the IFS detection model(s) 680, and the IFS control measure(s) 682.The database 670 can be implemented by a volatile memory (e.g., aSynchronous Dynamic Random Access Memory (SDRAM), Dynamic Random AccessMemory (DRAM), RAMBUS Dynamic Random Access Memory (RDRAM), etc.) and/ora non-volatile memory (e.g., flash memory). The database 670 canadditionally or alternatively be implemented by one or more double datarate (DDR) memories, such as DDR, DDR2, DDR3, DDR4, mobile DDR (mDDR),etc. The database 670 can additionally or alternatively be implementedby one or more mass storage devices such as hard disk drive(s), compactdisk drive(s), digital versatile disk drive(s), solid-state diskdrive(s), etc. While in the illustrated example the database 670 areillustrated as single databases, the database 670 can be implemented byany number and/or type(s) of databases. Furthermore, the data stored inthe database 670 can be in any data format such as, for example, binary,comma delimited, hexadecimal, JavaScript Object Notation (JSON), tabdelimited, Structured Query Language (SQL), XML, etc.

While an example implementation of the IFS controller 302 of FIGS. 3-5is illustrated in FIG. 6, one or more of the elements, processes and/ordevices illustrated in FIG. 6 can be combined, divided, re-arranged,omitted, eliminated and/or implemented in any other way. Further, theexample communication interface 610, the example IFS parameterdeterminer 620, the example IFS severity level parameter determiner 630,the example IFS detector 640, the example command generator 650, theexample alert generator 660, the example database 670 and/or, moregenerally, the example IFS controller of FIGS. 3-5 may be implemented byhardware, software, firmware and/or any combination of hardware,software and/or firmware. Thus, for example, any of the examplecommunication interface 610, the example IFS parameter determiner 620,the example IFS severity level parameter determiner 630, the example IFSdetector 640, the example command generator 650, the example alertgenerator 660, the example database 670 and/or, more generally, theexample IFS controller 302 could be implemented by one or more analog ordigital circuit(s), logic circuits, programmable processor(s),programmable controller(s), graphics processing unit(s) (GPU(s)),digital signal processor(s) (DSP(s)), application specific integratedcircuit(s) (ASIC(s)), programmable logic device(s) (PLD(s)) and/or fieldprogrammable logic device(s) (FPLD(s)). When reading any of theapparatus or system claims of this patent to cover a purely softwareand/or firmware implementation, at least one of the examplecommunication interface 610, the example IFS parameter determiner 620,the example IFS severity level parameter determiner 630, the example IFSdetector 640, the example command generator 650, the example alertgenerator 660, and/or the example database 670 is/are hereby expresslydefined to include a non-transitory computer readable storage device orstorage disk such as a memory, a digital versatile disk (DVD), a compactdisk (CD), a Blu-ray disk, etc. including the software and/or firmware.Further still, the example IFS controller 302 of FIGS. 3-5 may includeone or more elements, processes and/or devices in addition to, orinstead of, those illustrated in FIG. 6, and/or may include more thanone of any or all of the illustrated elements, processes and devices. Asused herein, the phrase “in communication,” including variationsthereof, encompasses direct communication and/or indirect communicationthrough one or more intermediary components, and does not require directphysical (e.g., wired) communication and/or constant communication, butrather additionally includes selective communication at periodicintervals, scheduled intervals, aperiodic intervals, and/or one-timeevents.

Flowcharts representative of example hardware logic, machine readableinstructions, hardware implemented state machines, and/or anycombination thereof for implementing the IFS controller 302 of FIGS. 3-6are shown in FIGS. 8-12. The machine readable instructions may be one ormore executable programs or portion(s) of an executable program forexecution by a computer processor such as the processor 1312 shown inthe example processor platform 1300 discussed below in connection withFIG. 13. The program may be embodied in software stored on anon-transitory computer readable storage medium such as a CD-ROM, afloppy disk, a hard drive, a DVD, a Blu-ray disk, or a memory associatedwith the processor 1312, but the entire program and/or parts thereofcould alternatively be executed by a device other than the processor1312 and/or embodied in firmware or dedicated hardware. Further,although the example program is described with reference to theflowcharts illustrated in FIGS. 8-12, many other methods of implementingthe example IFS controller 302 may alternatively be used. For example,the order of execution of the blocks may be changed, and/or some of theblocks described may be changed, eliminated, or combined. Additionallyor alternatively, any or all of the blocks may be implemented by one ormore hardware circuits (e.g., discrete and/or integrated analog and/ordigital circuitry, an FPGA, an ASIC, a comparator, anoperational-amplifier (op-amp), a logic circuit, etc.) structured toperform the corresponding operation without executing software orfirmware.

The machine readable instructions described herein may be stored in oneor more of a compressed format, an encrypted format, a fragmentedformat, a compiled format, an executable format, a packaged format, etc.Machine readable instructions as described herein may be stored as data(e.g., portions of instructions, code, representations of code, etc.)that may be utilized to create, manufacture, and/or produce machineexecutable instructions. For example, the machine readable instructionsmay be fragmented and stored on one or more storage devices and/orcomputing devices (e.g., servers). The machine readable instructions mayrequire one or more of installation, modification, adaptation, updating,combining, supplementing, configuring, decryption, decompression,unpacking, distribution, reassignment, compilation, etc. in order tomake them directly readable, interpretable, and/or executable by acomputing device and/or other machine. For example, the machine readableinstructions may be stored in multiple parts, which are individuallycompressed, encrypted, and stored on separate computing devices, whereinthe parts when decrypted, decompressed, and combined form a set ofexecutable instructions that implement a program such as that describedherein.

In another example, the machine readable instructions may be stored in astate in which they may be read by a computer, but require addition of alibrary (e.g., a dynamic link library (DLL)), a software development kit(SDK), an application programming interface (API), etc. in order toexecute the instructions on a particular computing device or otherdevice. In another example, the machine readable instructions may needto be configured (e.g., settings stored, data input, network addressesrecorded, etc.) before the machine readable instructions and/or thecorresponding program(s) can be executed in whole or in part. Thus, thedisclosed machine readable instructions and/or corresponding program(s)are intended to encompass such machine readable instructions and/orprogram(s) regardless of the particular format or state of the machinereadable instructions and/or program(s) when stored or otherwise at restor in transit.

The machine readable instructions described herein can be represented byany past, present, or future instruction language, scripting language,programming language, etc. For example, the machine readableinstructions may be represented using any of the following languages: C,C++, Java, C#, Perl, Python, JavaScript, HyperText Markup Language(HTML). Structured Query Language (SQL), Swift, etc.

As mentioned above, the example processes of FIGS. 8-12 may beimplemented using executable instructions (e.g., computer and/or machinereadable instructions) stored on a non-transitory computer and/ormachine readable medium such as a hard disk drive, a flash memory, aread-only memory, a compact disk, a digital versatile disk, a cache, arandom-access memory and/or any other storage device or storage disk inwhich information is stored for any duration (e.g., for extended timeperiods, permanently, for brief instances, for temporarily buffering,and/or for caching of the information). As used herein, the termnon-transitory computer readable medium is expressly defined to includeany type of computer readable storage device and/or storage disk and toexclude propagating signals and to exclude transmission media.

FIG. 8 is a flowchart representative of example machine readableinstructions 800 that can be executed to implement the IFS controller302 of FIGS. 3-6 to adjust an airflow contribution to the inlet 144 ofthe third turbofan 400 of FIGS. 4-5. The machine readable instructions800 of FIG. 8 begin at block 802, at which the IFS controller 302determines inlet flow separation (IFS) parameters based on sensor dataassociated with a turbofan. For example, the IFS parameter determiner620 (FIG. 6) can determine one or more of the IFS parameters 676 (FIG.6) based on the sensor data 674 (FIG. 6) associated with one(s) of theturbofans 300, 400, 430 (FIGS. 3-5). Example instructions that can beexecuted to implement block 802 are described below in connection withFIG. 9.

At block 804, the IFS controller 302 detects IFS based on the IFSparameters. For example, the IFS detector 640 (FIG. 6) can detect thesecond airflow 504 of FIG. 5, the IFS event represented by the arrows202 of FIG. 2, etc., based on the IFS parameter(s) 676, the IFS severitylevel parameter(s) 678 (FIG. 6), etc., and/or a combination thereof.Example instructions that can be executed to implement block 804 aredescribed below in connection with FIG. 10.

At block 806, the IFS controller 302 determines whether IFS is detectedbased on the IFS parameters. For example, the IFS detector 640 may notdetect IFS based on the IFS parameter(s) 676, the IFS severity levelparameter(s) 678, etc., and/or a combination thereof. In other examples,the IFS detector 640 may detect IFS based on the IFS parameter(s) 676,the IFS severity level parameter(s) 678, etc., and/or a combinationthereof.

If, at block 806, the IFS controller 302 determines that IFS is notdetected, control proceeds to block 816 to determine whether to continuemonitoring the turbofan. If, at block 806, the IFS controller 302determines that IFS is detected, then, at block 808, the IFS controller302 identifies IFS control measure(s) based on IFS severity levelparameters. For example, the IFS severity level parameter determiner 630(FIG. 6) can determine one(s) of the IFS severity level parameters 678(FIG. 6). In such examples, the command generator 650 (FIG. 6) canidentify one(s) of the IFS control measure(s) 682 (FIG. 6) based on theIFS severity level parameter(s) 678. Example instructions that can beexecuted to implement block 808 are described below in connection withFIG. 11.

At block 810, the IFS controller 302 determines whether IFS controlmeasure(s) have been identified. For example, the command generator 650can determine that there are no IFS control measure(s) to deploy inresponse to determining that the IFS severity level parameter(s) 678 donot indicate IFS. In other examples, the command generator 650 candetermine to invoke one(s) of the actuators 402, 404 (FIGS. 4A and/or4B) to adjust the IFS based on the IFS severity level parameter(s) 678indicating a low, medium, or high IFS at the inlet portion 144.

If, at block 810, the IFS controller 302 determines that there are noIFS control measure(s) identified, control proceeds to block 816 todetermine whether to continue monitoring the turbofan. If, at block 810,the IFS controller 302 determines that there is/are IFS controlmeasure(s) identified, then, at block 812, the IFS controller 302controls actuator(s) to adjust airflow contribution(s) to the inlet 144of the turbofan 300, 400, 430. For example, the command generator 650can transmit a command to the actuators 402, 404 to adjust positions toadjust airflow contributions from the first section 406 and/or thesecond section 408 to the third section 410 of FIGS. 4-5.

At block 814, the IFS controller 302 generates an alert. For example,the alert generator 660 (FIG. 6) can generate an alert including atleast one of the flight data 672 (FIG. 6), the sensor data 674, one(s)of the IFS parameter(s) 676, one(s) of the IFS severity levelparameter(s) 678, or deployed one(s) of the IFS control measure(s) 682.In such examples, the alert generator 660 can transmit the alert to adisplay for presentation to a pilot in a cockpit of an aircraft, storethe alert in the database 670 (FIG. 6) for maintenance tasks orimprovements to be conducted on the turbofan 300, 400, 430, etc., and/ora combination thereof.

At block 816, the IFS controller 302 determines whether to continuemonitoring the turbofan. For example, the communication interface 610(FIG. 6) can determine that the turbofan 300, 400, 430 is not in flight(e.g., an aircraft has landed on a ground surface, taxiing to a gate,parked at the gate, etc.) and, thus, determines not to continuemonitoring the turbofan 300, 400, 430. In other examples, thecommunication interface 610 can determine to continue monitoring theturbofan 300, 400, 430 to determine if the IFS has been reduced and/orotherwise eliminated in response to the IFS control measure(s) 682deployed at block 810.

If, at block 816, the IFS controller 302 determines to continuemonitoring the turbofan, control returns to block 802 to determine theIFS parameters based on the sensor date associated with the turbofan.If, at block 816, the IFS controller 302 determines not to continuemonitoring the turbofan, the machine readable instructions 800 of FIG. 8conclude.

FIG. 9 is a flowchart representative of example machine readableinstructions 900 that can be executed to implement the IFS controller302 of FIGS. 3-6 to determine the IFS parameters 676 of FIG. 6 based onthe sensor data 674 of FIG. 6 associated with the second turbofan 300 ofFIG. 3 and/or the third turbofan 400 FIGS. 4-5. The machine readableinstructions 900 of FIG. 9 can be executed to implement block 802 ofFIG. 8.

The machine readable instructions 900 of FIG. 9 begin at block 902, atwhich the IFS controller 302 obtains first air pressure data from firstair pressure sensors at nacelle outer lips. For example, thecommunication interface 610 (FIG. 6) can obtain first air pressure datafrom the first pressure sensor 304 and second air pressure data from thethird pressure sensor 308.

At block 904, the IFS controller 302 determines first air pressurevalues at the nacelle outer lips based on the first air pressure data.For example, the IFS parameter determiner 620 (FIG. 6) can determine afirst air pressure value at the first outer lip 208 based on the firstair pressure data and a second air pressure value at the second outerlip 212 based on the second air pressure data.

At block 906, the IFS controller 302 obtains second air pressure datafrom second air pressure sensors at nacelle inner lips. For example, thecommunication interface 610 can obtain third air pressure data from thesecond pressure sensor 306 and fourth air pressure data from the fourthpressure sensor 310.

At block 908, the IFS controller 302 determines second air pressurevalues at the nacelle inner lips based on the second air pressure data.For example, the IFS parameter determiner 620 can determine a third airpressure value at the first inner lip 210 based on the third airpressure data and a fourth air pressure value at the second inner lip214 based on the fourth air pressure data.

At block 910, the IFS controller 302 obtains altitude data and speeddata from a database. For example, the IFS parameter determiner 620 canobtain altitude data and the speed data from the flight data 672 (FIG.6) stored in the database 670 (FIG. 6).

At block 912, the IFS controller 302 determines air density based on thealtitude data. For example, the IFS parameter determiner 620 candetermine the air density based on the altitude data.

At block 914, the IFS controller 302 determines a Mach number based onthe speed data. For example, the IFS parameter determiner 620 candetermine the Mach number based on the speed data.

At block 916, the IFS controller 302 obtains acceleration data fromacceleration sensors. For example, the communication interface 610 canobtain acceleration data from one or more acceleration sensors 316, 318coupled to one or more bearings 317, 319 of the bearing section 320 ofthe engine 104 of FIGS. 3-5.

At block 918, the IFS controller 302 determines bearing load(s) based onthe acceleration data. For example, the IFS parameter determiner 620 candetermine a first load on the first bearing 317, a second load on thesecond bearing 319, etc., of the engine 104 based on the accelerationdata. In response to determining the bearing load(s) based on theacceleration data at block 918, control returns to block 804 of themachine readable instructions 800 of FIG. 8 to detect IFS based on theIFS parameters.

FIG. 10 is a flowchart representative of example machine readableinstructions 1000 that can be executed to implement the IFS controller302 of FIGS. 3-6 to detect IFS based on the IFS parameters. The machinereadable instructions 1000 of FIG. 10 can be executed to implement block804 of FIG. 8.

The machine readable instructions 1000 of FIG. 10 begin at block 1002,at which the IFS controller 302 determines air flow direction(s) basedon difference(s) between outer nacelle pressure(s) and a pressurethreshold. For example, the IFS severity level parameter determiner 630(FIG. 6) can determine a first flow direction of airflow at the firstouter lip 208 based on a difference between the first pressure valuefrom the first pressure sensor 304 and a pressure threshold. In suchexamples, the IFS severity level parameter determiner 630 can determinea second flow direction of airflow at the second outer lip 212 based ona difference between the second pressure value from the third pressuresensor 308 and the pressure threshold.

At block 1004, the IFS controller 302 determines first IFS severitylevel parameter(s) based on the air flow direction(s) and a first weightfactor. For example, the IFS severity level parameter determiner 630 candetermine the first IFS severity level parameter 702 (FIG. 7) associatedwith the first nacelle 134 based on the air flow direction at the firstouter lip 208 and the first weight factor 708 (FIG. 7). In suchexamples, the IFS severity level parameter determiner 630 can determinethe first IFS severity level parameter 702 associated with the secondnacelle 135 based on the air flow direction at the second outer lip 212and the first weight factor 708.

At block 1006, the IFS controller 302 determines pressure difference(s)between outer nacelle pressure(s) and inner nacelle pressure(s). Forexample, the IFS severity level parameter determiner 630 can determine afirst pressure difference across surfaces of the first nacelle 134 basedon a first difference between the first pressure value from the firstpressure sensor 304 and the second pressure value from the secondpressure sensor 306. In such examples, the IFS severity level parameterdeterminer 630 can determine a second pressure difference acrosssurfaces of the second nacelle 135 based on a second difference betweenthe third pressure value from the third pressure sensor 308 and thefourth pressure value from the fourth pressure sensor 310.

At block 1008, the IFS controller 302 determines second IFS severitylevel parameter(s) based on the pressure difference(s) and a secondweight factor. For example, the IFS severity level parameter determiner630 can determine the second IFS severity level parameter 704 (FIG. 7)associated with the first nacelle 134 based on the first pressuredifference across at the first outer lip 208 and the first inner lip 210and the second weight factor 710 (FIG. 7). In such examples, the IFSseverity level parameter determiner 630 can determine the second IFSseverity level parameter 704 associated with the second nacelle 135based on the second pressure difference across at the second outer lip212 and the second inner lip 214 and the second weight factor 710.

At block 1010, the IFS controller 302 determines an engine vibratoryresponse based on bearing load(s). For example, the IFS severity levelparameter determiner 630 can determine the third IFS severity levelparameter 706 (FIG. 7) based on an engine vibratory response generatedbased on acceleration data from one(s) of the acceleration sensors 316,318.

At block 1012, the IFS controller 302 determines a third IFS severitylevel parameter based on the engine vibratory response and a thirdweight factor. For example, the IFS severity level parameter determiner630 can determine the third IFS severity level parameter 706 associatedwith the engine 104 based on the engine vibratory response associatedwith the engine 104 and the third weight factor 712 (FIG. 7).

At block 1014, the IFS controller 302 determines a probability densityfunction based on at least the first through third severity levelparameters. For example, the IFS detector 640 (FIG. 6) can determine aprobability density function based on one or more of the first IFSseverity level parameters 702, one or more of the second IFS severitylevel parameters 704, one or more of the third IFS severity levelparameters, etc.

At block 1016, the IFS controller 302 compares the probability densityfunction to stored probability density function(s). For example, the IFSdetector 640 can compare the probability density function to the firstprobability density function 714 (FIG. 7), the second probabilitydensity function 716 (FIG. 7), and/or the third probability densityfunction 718 (FIG. 7). In such examples, the first through thirdprobability density functions 714, 716, 718 can be stored in thedatabase 670 (FIG. 6) as the IFS detection model(s) 680.

At block 1018, the IFS controller 302 detects IFS based on thecomparison(s). For example, the IFS detector 640 can detect and/orotherwise determine an existence or presence of IFS at the inlet 144 ofFIGS. 1-5 based on the comparisons executed at block 1016. In responseto detecting IFS based on the comparisons at block 1018, control returnsto block 806 of the machine readable instructions 800 of FIG. 8 todetermine whether IFS is detected.

FIG. 11 is a flowchart representative of example machine readableinstructions 1100 that can be executed to implement the IFS controller302 of FIGS. 3-6 to identify the IFS control measure(s) 682 (FIG. 6)based on the IFS severity level parameter(s) 678 (FIG. 6). The machinereadable instructions 1100 of FIG. 11 can be executed to implement block808 of FIG. 8.

The machine readable instructions 1100 of FIG. 11 begin at block 1102,at which the IFS controller 302 determines whether the IFS severitylevel parameter(s) are indicative of no IFS. For example, the IFSdetector 640 (FIG. 6) can determine that there is no IFS at the inlet144 based on the IFS severity level parameter(s) 678. In other examples,the IFS detector 640 can determine that there is IFS at the inlet 144based on the IFS severity level parameter(s) 678.

If, at block 1102, the IFS controller 302 determines that the IFSseverity level parameter(s) is/are indicative of no IFS, then, at block1104, the IFS controller 302 determines that there are no IFS controlmeasure(s) to deploy. For example, the command generator 650 (FIG. 6)can determine not to deploy one(s) of the IFS control measure(s) 682stored in the database 670 (FIG. 6) based on the IFS severity levelparameter(s) 678. In response to determining that there are no IFScontrol measure(s) to deploy at block 1104, control returns to block 810of the machine readable instructions 800 of FIG. 8 to determine whetherIFS control measure(s) have been identified.

If, at block 1102, the IFS controller 302 determines that the IFSseverity level parameter(s) is/are not indicative of no IFS, controlproceeds to block 1106 to determine whether the IFS severity levelparameter(s) are indicative of high IFS. For example, the IFS detector640 can determine that there is a substantially high IFS at the inlet144. In such examples, the IFS detector 640 can determine that adetermined probability density function based on the IFS severity levelparameters 702, 704, 706 of FIG. 7 closely matches (e.g., is within apre-defined tolerance) and/or otherwise corresponds to the thirdprobability density function 718 (FIG. 7).

If, at block 1106, the IFS controller 302 determines that the IFSseverity level parameter(s) is/are indicative of high IFS, then, atblock 1108, the IFS controller 302 controls actuator(s) to facilitatehigh core airflow contribution and low fan airflow contribution. Forexample, the command generator 650 can map the detection of high IFS tothe first one of the IFS control measure(s) 682 to effectuate a highairflow contribution from the first section 406 and a low airflowcontribution from the second section 408 to be delivered to the thirdsection 410. In such examples, the command generator 650 can cause theactuators 402, 404 to increase airflow from the first section 406 anddecrease airflow from the second section 408. In response to controllingthe actuator(s) to facilitate high core airflow contribution and low fanairflow contribution at block 1108, control returns to block 810 of themachine readable instructions 800 of FIG. 8 to determine whether IFScontrol measure(s) have been identified.

If, at block 1106, the IFS controller 302 determines that the IFSseverity level parameter(s) is/are not indicative of high IFS, controlproceeds to block 1110 to determine whether the IFS severity levelparameter(s) is/are indicative of medium IFS. For example, the IFSdetector 640 can determine that there is a medium level, quantity, etc.,of IFS at the inlet 144. In such examples, the IFS detector 640 candetermine that a determined probability density function based on theIFS severity level parameters 702, 704, 706 of FIG. 7 closely matches(e.g., is within a pre-defined tolerance) and/or otherwise correspondsto the second probability density function 716 (FIG. 7).

If, at block 1110, the IFS controller 302 determines that the IFSseverity level parameter(s) is/are indicative of medium IFS, then, atblock 1112, the IFS controller 302 controls actuator(s) to facilitatemedium core airflow contribution and medium fan airflow contribution.For example, the command generator 650 can map the detection of mediumIFS to the second one of the IFS control measure(s) 682 to effectuate amedium airflow contribution from the first section 406 and a mediumairflow contribution from the second section 408 to be introduced to thethird section 410. In such examples, the command generator 650 can causethe actuators 402, 404 to adjust airflow from the first section 406(e.g., decrease from a high quantity of airflow to a medium quantity ofairflow, increase from a low quantity of airflow to a medium quantity ofairflow, etc.) and adjust airflow from the second section 408 (e.g.,increase from a low quantity of airflow to a medium quantity of airflow,decrease from a high quantity of airflow to a medium quantity ofairflow, etc.). In response to controlling the actuator(s) to facilitatemedium core airflow contribution and medium fan airflow contribution atblock 1112, control returns to block 810 of the machine readableinstructions 800 of FIG. 8 to determine whether IFS control measure(s)have been identified.

If, at block 1110, the IFS controller 302 determines that the IFSseverity level parameter(s) is/are not indicative of medium IFS, controlproceeds to block 1114 to determine whether the IFS severity levelparameter(s) is/are indicative of low IFS. For example, the IFS detector640 can determine that there is a low IFS at the inlet 144. In suchexamples, the IFS detector 640 can determine that a determinedprobability density function based on the IFS severity level parameters702, 704, 706 of FIG. 7 does not closely match (e.g., is within apre-defined tolerance) and/or otherwise correspond to any of theprobability density functions 714, 716, 718 (FIG. 7) or closely matcheswith a probability density function associated with low IFS.

If, at block 1114, the IFS controller 302 determines that the IFSseverity level parameter(s) is/are not indicative of low IFS, controlreturns to block 810 of the machine readable instructions 800 of FIG. 8to determine whether IFS control measure(s) have been identified. If, atblock 1114, the IFS controller 302 determines that the IFS severitylevel parameter(s) is/are indicative of low IFS, then, at block 1116,the IFS controller 302 controls actuator(s) to facilitate low coreairflow contribution and high fan airflow contribution. For example, thecommand generator 650 can map the detection of low IFS to the third oneof the IFS control measure(s) 682 to cause a low airflow contributionfrom the first section 406 and a high airflow contribution from thesecond section 408 to be introduced to the third section 410. In suchexamples, the command generator 650 can cause the actuators 402, 404 todecrease airflow from the first section 406 and increase airflow fromthe second section 408. In response to controlling the actuator(s) tofacilitate low core airflow contribution and high fan airflowcontribution at block 1116, control returns to block 810 of the machinereadable instructions 800 of FIG. 8 to determine whether IFS controlmeasure(s) have been identified.

FIG. 12 is a flowchart representative of example machine readableinstructions 1200 that can be executed to implement the IFS controller302 of FIGS. 3-6 to adjust an airflow contribution to an inlet of thethird turbofan 400 of FIG. 4A and/or the fourth turbofan 430 of FIGS. 4Band/or 5. The machine readable instructions 1200 of FIG. 12 begin atblock 1202, at which the IFS controller 302 determines whether an inletflow separation (IFS) command has been obtained. For example, thecommunication interface 610 (FIG. 6) can obtain an IFS command from anaircraft coupled to the third turbofan 400 of FIG. 4A, a pilotcontrolling the aircraft from a cockpit of the aircraft, etc. In suchexamples, the IFS command can be to increase an airflow contributionfrom the first section 406 or the second section 408 to the thirdsection 410. In other examples, the IFS command can be to decrease anairflow contribution from the first section 406 or the second section408 to the third section 410.

If, at block 1202, the IFS controller 302 determines that an IFS commandhas not been obtained, control waits at block 1202 for an IFS command.If, at block 1202, the IFS controller 302 determines that the IFScommand has been obtained, control proceeds to block 1204 to identifyIFS control measure(s) based on the IFS command. For example, thecommand generator 650 (FIG. 6) can map the command to one(s) of the IFScontrol measure(s) 682 (FIG. 6) to determine one or more action(s) toexecute.

At block 1206, the IFS controller 302 determines whether the IFS controlmeasure(s) include(s) increasing aft of fan airflow contribution. Forexample, the command generator 650 can determine that the IFS controlmeasure(s) 682 based on the IFS command includes controlling one(s) ofthe actuators 402, 404 to increase an airflow contribution from thesecond section 408 to the third section 410.

If, at block 1206, the IFS controller 302 determines that the IFScontrol measure(s) do not include increasing aft of fan airflowcontribution, control proceeds to block 1210 to determine whether theIFS control measure(s) include(s) decreasing aft of fan airflowcontribution. If, at block 1206, the IFS controller 302 determines thatthe IFS control measure(s) include(s) increasing aft of fan airflowcontribution, then, at block 1208, the IFS controller 302 controlsactuator(s) to increase airflow contribution(s) from aft of the fan toan inlet of the turbofan. For example, the command generator 650 (FIG.6) can transmit a command to the first actuator 402 and/or the secondactuator 404 to facilitate an increase in airflow from the secondsection 408 to the third section 410.

At block 1210, the IFS controller 302 determines whether the IFS controlmeasure(s) include(s) decreasing aft of fan airflow contribution. Forexample, the command generator 650 can determine that the IFS controlmeasure(s) 682 based on the IFS command includes controlling one(s) ofthe actuators 402, 404 to decrease an airflow contribution from thesecond section 408 to the third section 410.

If, at block 1210, the IFS controller 302 determines that the IFScontrol measure(s) do not include decreasing aft of fan airflowcontribution, control proceeds to block 1214 to store data associatedwith action(s) in a database. If, at block 1210, the IFS controller 302determines that the IFS control measure(s) include(s) decreasing aft offan airflow contribution, then, at block 1212, the IFS controller 302controls actuator(s) to decrease airflow contribution(s) from aft of thefan to an inlet of the turbofan. For example, the command generator 650can transmit a command to the first actuator 402 and/or the secondactuator 404 to facilitate a decrease in airflow from the second section408 to the third section 410.

At block 1214, the IFS controller 302 stores data associated withaction(s) in a database. For example, the alert generator 660 (FIG. 6)can record and/or otherwise store the flight data 672 (FIG. 6) and/orthe sensor data 674 (FIG. 6) associated with time(s) before, during,and/or after actuation(s) of the first actuator 402 and/or the secondactuator 404 in the database 670 (FIG. 6). In such examples, the alertgenerator 660 can record which one(s) of the actuators 402, 404 areinvoked in response to the IFS command, position(s) of one(s) of theactuators 402, 404, etc., and/or a combination thereof.

At block 1216, the IFS controller 302 determines whether to continuemonitoring the turbofan. If, at block 1216, the IFS controller 302determines to continue monitoring the turbofan, control returns to block1202 to determine whether another IFS command has been obtained. If, atblock 1216, the IFS controller 302 determines not to continue monitoringthe turbofan, the machine readable instructions 1200 of FIG. 12conclude.

FIG. 13 is a block diagram of an example processor platform 1300structured to execute the instructions of FIGS. 8-12 to implement theIFS controller 302 of FIGS. 3-6. The processor platform 1300 can be, forexample, an electronic control unit (ECU), an electronic engine control(EEC) unit, a full-authority digital engine control (FADEC) unit, aself-learning machine (e.g., a neural network), or any other type ofcomputing device.

The processor platform 1300 of the illustrated example includes aprocessor 1312. The processor 1312 of the illustrated example ishardware. For example, the processor 1312 can be implemented by one ormore integrated circuits, logic circuits, microprocessors, GPUs, DSPs,or controllers from any desired family or manufacturer. The hardwareprocessor can be a semiconductor based (e.g., silicon based) device. Inthis example, the processor 1312 implements the IFS parameter determiner620, the IFS severity level parameter determiner 630, the IFS detector640, the command generator 650, and the alert generator 660 of FIG. 6.In FIG. 13, the IFS parameter determiner 620 is depicted as “IFS PARAMDETER,” the IFS severity level parameter determiner 630 is depicted as“IFS SL PARAM DETER,” and the command generator 650 is depicted as “CMDGENERATOR” 650.

The processor 1312 of the illustrated example includes a local memory1313 (e.g., a cache). The processor 1312 of the illustrated example isin communication with a main memory including a volatile memory 1314 anda non-volatile memory 1316 via a bus 1318. The volatile memory 1314 canbe implemented by Synchronous Dynamic Random Access Memory (SDRAM),Dynamic Random Access Memory (DRAM), RAMBUS® Dynamic Random AccessMemory (RDRAM®) and/or any other type of random access memory device.The non-volatile memory 1316 can be implemented by flash memory and/orany other desired type of memory device. Access to the main memory 1314,1316 is controlled by a memory controller.

The processor platform 1300 of the illustrated example also includes aninterface circuit 1320. The interface circuit 1320 can be implemented byany type of interface standard, such as an Ethernet interface, auniversal serial bus (USB), a Bluetooth® interface, a near fieldcommunication (NFC) interface, and/or a PCI express interface. In thisexample, the interface circuit 1320 implements the communicationinterface 610 of FIG. 6.

In the illustrated example, one or more input devices 1322 are connectedto the interface circuit 1320. The input device(s) 1322 permit(s) a userto enter data and/or commands into the processor 1312. The inputdevice(s) 1322 can be implemented by, for example, an audio sensor, amicrophone, a camera (still or video), a keyboard, a button, a mouse, atouchscreen, a track-pad, a trackball, an isopoint device, and/or avoice recognition system.

One or more output devices 1324 are also connected to the interfacecircuit 1320 of the illustrated example. The output devices 1324 can beimplemented, for example, by display devices (e.g., a light emittingdiode (LED), an organic light emitting diode (OLED), a liquid crystaldisplay (LCD), a cathode ray tube (CRT) display, an in-place switching(IPS) display, a touchscreen, etc.), a tactile output device, a printerand/or speaker. The interface circuit 1320 of the illustrated example,thus, typically includes a graphics driver card, a graphics driver chipand/or a graphics driver processor.

The interface circuit 1320 of the illustrated example also includes acommunication device such as a transmitter, a receiver, a transceiver, amodem, a residential gateway, a wireless access point, and/or a networkinterface to facilitate exchange of data with external machines (e.g.,computing devices of any kind) via a network 1326. The communication canbe via, for example, an Ethernet connection, a digital subscriber line(DSL) connection, a telephone line connection, a coaxial cable system, asatellite system, a line-of-site wireless system, a cellular telephonesystem, etc.

The processor platform 1300 of the illustrated example also includes oneor more mass storage devices 1328 for storing software and/or data.Examples of such mass storage devices 1328 include floppy disk drives,hard drive disks, compact disk drives, Blu-ray disk drives, redundantarray of independent disks (RAID) systems, and digital versatile disk(DVD) drives. In this example, the one or more mass storage devices 1328implement the database 670, the flight data 672, the sensor data 674,the IFS parameter(s) 676, the IFS severity level parameter(s) 678, theIFS detection model(s) 680, and the IFS control measure(s) 682 of FIG.6. In FIG. 13, the IFS severity level parameter(s) 678 are depicted as“IFS SL PARAM(S),” the IFS detection model(s) 680 are depicted as“DETECT MODEL(S),” and the IFS control measure(s) 682 are depicted as“CNTL MEASURE(S).”

The machine executable instructions 1332 of FIGS. 8-12 can be stored inthe mass storage device 1328, in the volatile memory 1314, in thenon-volatile memory 1316, and/or on a removable non-transitory computerreadable storage medium such as a CD or DVD.

From the foregoing, it will be appreciated that example methods,apparatus, and articles of manufacture have been disclosed that detectand/or control air flow separation of an engine. The example methods,apparatus, and articles of manufacture determine IFS parameters based onflight data, sensor data, etc., and can determine IFS severity levelparameters based on the IFS parameters. The example methods, apparatus,and articles of manufacture can detect IFS and/or a quantificationand/or severity of the IFS based on the IFS parameters, the IFS severitylevel parameters, etc. The example methods, apparatus, and articles ofmanufacture can control one or more actuators to adjust airflow bleedsto an inlet section of the engine based on the IFS detection.Advantageously, the example methods, apparatus, and articles ofmanufacture can improve the reliability and/or operating lifetime ofcomponent(s) of the engine and/or, more generally, the engine, bydetecting IFS and reducing and/or otherwise eliminating IFS in responseto the detection.

The disclosed methods, apparatus, and articles of manufacture improvethe efficiency of using a computing device, such as an ECU, a FADEC,etc., by pre-processing data such as IFS parameters, IFS severity levelparameters, etc., prior to detecting IFS. Advantageously, bypre-processing the data, the disclosed methods, apparatus, and articlesof manufacture can detect IFS using reduced computing resources comparedto detecting IFS using non-processed data. The disclosed methods,apparatus and articles of manufacture are accordingly directed to one ormore improvement(s) in the functioning of a computer.

Further aspects of the invention are provided by the subject matter ofthe following clauses:

1. An apparatus comprising hardware, and memory including instructionsthat, when executed, cause the hardware to at least determine an inletflow separation parameter based on a first pressure value from a firstpressure sensor included in a nacelle of a turbofan and a secondpressure value from a second pressure sensor included in the nacelle,determine a severity level parameter based on the inlet flow separationparameter, the severity level parameter based on a difference betweenthe first pressure value and the second pressure value, and adjust acontribution of airflow from aft of a fan of the turbofan based on theseverity level parameter.

2. The apparatus of any preceding clause wherein the first pressuresensor is coupled to an outer lip of the nacelle, the severity levelparameter is a first severity level parameter, and the hardware todetermine an airflow direction at the outer lip based on a differencebetween the first pressure value and a threshold, determine a secondseverity level parameter based on the difference and a weight value, anddetect inlet flow separation at an inlet of turbofan based on the firstseverity level parameter and the second severity level parameter.

3. The apparatus of any preceding clause wherein the hardware is todetermine a first probability density function based on the firstseverity level parameter and the second severity level parameter,compare the first probability density function to a second probabilitydensity function stored in a database, and detect the inlet flowseparation at the inlet of the turbofan based on the comparison.

4. The apparatus of any preceding clause wherein the first pressuresensor is coupled to an outer lip of the nacelle, the second pressuresensor is coupled to an inner lip of the nacelle, the severity levelparameter corresponding to a nacelle inlet pressure difference, and thehardware to determine the nacelle inlet pressure difference based on adifference between the first pressure value and the second pressurevalue, determine the severity level parameter based on the nacelle inletpressure difference and a weight value, and detect inlet flow separationat an inlet of turbofan based on the severity level parameter.

5. The apparatus of any preceding clause wherein the severity levelparameter is a first severity level parameter, and the hardware toobtain acceleration data from an accelerometer coupled to a bearing ofthe turbofan, determine a vibratory response of the turbofan based onthe acceleration data, determine a second severity level parameter basedon the vibratory response and a weight value, and detect inlet flowseparation at an inlet of turbofan based on the first severity levelparameter and the second severity level parameter.

6. The apparatus of any preceding clause wherein the first pressuresensor is coupled to an outer lip of the nacelle, the second pressuresensor is coupled to an inner lip of the nacelle, and the hardware toobtain altitude data and speed data from an aircraft coupled to theturbofan, determine an air density based on the altitude data, determinea Mach number based on the speed data, and determine the inlet flowseparation parameter based on at least one of the first pressure value,the second pressure value, the air density, or the Mach number.

7. The apparatus of any preceding clause wherein the hardware is toadjust the contribution of airflow from aft of the fan by controlling anactuator included in the nacelle based on the severity level parameter,the actuator to move from a first position to a second position toadjust the contribution of the airflow from aft of the fan to forward ofthe fan.

8. An apparatus comprising an inlet flow separation parameter determinerto determine an inlet flow separation parameter based on a firstpressure value from a first pressure sensor included in a nacelle of aturbofan and a second pressure value from a second pressure sensorincluded in the nacelle, an inlet flow separation severity levelparameter determiner to determine a severity level parameter based onthe inlet flow separation parameter, the severity level parameter basedon a difference between the first pressure value and the second pressurevalue, and a command generator to adjust a contribution of airflow fromaft of a fan of the turbofan based on the severity level parameter.

9. The apparatus of any preceding clause wherein the first pressuresensor is coupled to an outer lip of the nacelle, the severity levelparameter is a first severity level parameter, the inlet flow separationseverity level parameter determiner to determine an airflow direction atthe outer lip based on a difference between the first pressure value anda threshold, and determine a second severity level parameter based onthe difference and a weight value, and further including an inlet flowseparation detector to detect inlet flow separation at an inlet ofturbofan based on the first severity level parameter and the secondseverity level parameter.

10. The apparatus of any preceding clause wherein the inlet flowseparation detector is to determine a first probability density functionbased on the first severity level parameter and the second severitylevel parameter, compare the first probability density function to asecond probability density function stored in a database, and detect theinlet flow separation at the inlet of the turbofan based on thecomparison.

11. The apparatus of any preceding clause wherein the first pressuresensor is coupled to an outer lip of the nacelle, the second pressuresensor is coupled to an inner lip of the nacelle, the severity levelparameter corresponding to a nacelle inlet pressure difference, theinlet flow separation severity level parameter determiner to determinethe nacelle inlet pressure difference based on a difference between thefirst pressure value and the second pressure value, determine theseverity level parameter based on the nacelle inlet pressure differenceand a weight value, and further including an inlet flow separationdetector to detect inlet flow separation at an inlet of turbofan basedon the severity level parameter.

12. The apparatus of any preceding clause wherein the severity levelparameter is a first severity level parameter, further including acollection engine to obtain acceleration data from an accelerometercoupled to a bearing of the turbofan, the inlet flow separation severitylevel parameter determiner is to determine a vibratory response of theturbofan based on the acceleration data, determine a second severitylevel parameter based on the vibratory response and a weight value, andfurther including an inlet flow separation detector to detect inlet flowseparation at an inlet of turbofan based on the first severity levelparameter and the second severity level parameter.

13. The apparatus of any preceding clause wherein the first pressuresensor is coupled to an outer lip of the nacelle, the second pressuresensor is coupled to an inner lip of the nacelle, and further includinga collection engine to obtain altitude data and speed data from anaircraft coupled to the turbofan, and the inlet flow separationparameter determiner to determine an air density based on the altitudedata, determine a Mach number based on the speed data, and determine theinlet flow separation parameter based on at least one of the firstpressure value, the second pressure value, the air density, or the Machnumber.

14. The apparatus of any preceding clause wherein the command generatoris to adjust the contribution of airflow from aft of the fan bycontrolling an actuator included in the nacelle based on the severitylevel parameter, the command generator to invoke the actuator to movefrom a first position to a second position to adjust the contribution ofthe airflow from aft of the fan to forward of the fan.

15. A non-transitory computer readable storage medium comprisinginstructions that, when executed, cause at least one processor to atleast determine an inlet flow separation parameter based on a firstpressure value from a first pressure sensor included in a nacelle of aturbofan and a second pressure value from a second pressure sensorincluded in the nacelle, determine a severity level parameter based onthe inlet flow separation parameter, the severity level parameter basedon a difference between the first pressure value and the second pressurevalue, and adjust a contribution of airflow from aft of a fan of theturbofan based on the severity level parameter.

16. The non-transitory computer readable storage medium of any precedingclause wherein the first pressure sensor is coupled to an outer lip ofthe nacelle, the severity level parameter is a first severity levelparameter, and the instructions, when executed, cause the at least oneprocessor to determine an airflow direction at the outer lip based on adifference between the first pressure value and a threshold, determine asecond severity level parameter based on the difference and a weightvalue, and detect inlet flow separation at an inlet of turbofan based onthe first severity level parameter and the second severity levelparameter.

17. The non-transitory computer readable storage medium of any precedingclause wherein the instructions, when executed, cause the at least oneprocessor to determine a first probability density function based on thefirst severity level parameter and the second severity level parameter,compare the first probability density function to a second probabilitydensity function stored in a database, and detect the inlet flowseparation at the inlet of the turbofan based on the comparison.

18. The non-transitory computer readable storage medium of any precedingclause wherein the first pressure sensor is coupled to an outer lip ofthe nacelle, the second pressure sensor is coupled to an inner lip ofthe nacelle, the severity level parameter corresponding to a nacelleinlet pressure difference, and the instructions, when executed, causethe at least one processor to determine the nacelle inlet pressuredifference based on a difference between the first pressure value andthe second pressure value, determine the severity level parameter basedon the nacelle inlet pressure difference and a weight value, and detectinlet flow separation at an inlet of turbofan based on the severitylevel parameter.

19. The non-transitory computer readable storage medium of any precedingclause wherein the severity level parameter is a first severity levelparameter, and the instructions, when executed, cause the at least oneprocessor to obtain acceleration data from an accelerometer coupled to abearing of the turbofan, determine a vibratory response of the turbofanbased on the acceleration data, determine a second severity levelparameter based on the vibratory response and a weight value, and detectinlet flow separation at an inlet of turbofan based on the firstseverity level parameter and the second severity level parameter.

20. The non-transitory computer readable storage medium of any precedingclause wherein the first pressure sensor is coupled to an outer lip ofthe nacelle, the second pressure sensor is coupled to an inner lip ofthe nacelle, and the instructions, when executed, cause the at least oneprocessor to obtain altitude data and speed data from an aircraftcoupled to the turbofan, determine an air density based on the altitudedata, determine a Mach number based on the speed data, and determine theinlet flow separation parameter based on at least one of the firstpressure value, the second pressure value, the air density, or the Machnumber.

21. The non-transitory computer readable storage medium of any precedingclause wherein the instructions, when executed, cause the at least oneprocessor to adjust the contribution of airflow from aft of the fan bycontrolling an actuator included in the nacelle based on the severitylevel parameter, the actuator to move from a first position to a secondposition to adjust the contribution of the airflow from aft of the fanto forward of the fan.

22. A method comprising determining an inlet flow separation parameterbased on a first pressure value from a first pressure sensor included ina nacelle of a turbofan and a second pressure value from a secondpressure sensor included in the nacelle, determining a severity levelparameter based on the inlet flow separation parameter, the severitylevel parameter based on a difference between the first pressure valueand the second pressure value, and adjusting a contribution of airflowfrom aft of a fan of the turbofan based on the severity level parameter.

23. The method of any preceding clause wherein the first pressure sensoris coupled to an outer lip of the nacelle, the severity level parameteris a first severity level parameter, and further including determiningan airflow direction at the outer lip based on a difference between thefirst pressure value and a threshold, determining a second severitylevel parameter based on the difference and a weight value, anddetecting inlet flow separation at an inlet of turbofan based on thefirst severity level parameter and the second severity level parameter.

24. The method of any preceding clause further including determining afirst probability density function based on the first severity levelparameter and the second severity level parameter, comparing the firstprobability density function to a second probability density functionstored in a database, and detecting the inlet flow separation at theinlet of the turbofan based on the comparison.

25. The method of any preceding clause wherein the first pressure sensoris coupled to an outer lip of the nacelle, the second pressure sensor iscoupled to an inner lip of the nacelle, the severity level parametercorresponding to a nacelle inlet pressure difference, and furtherincluding determining the nacelle inlet pressure difference based on adifference between the first pressure value and the second pressurevalue, determining the severity level parameter based on the nacelleinlet pressure difference and a weight value, and detecting inlet flowseparation at an inlet of turbofan based on the severity levelparameter.

26. The method of any preceding clause wherein the severity levelparameter is a first severity level parameter, and further includingobtaining acceleration data from an accelerometer coupled to a bearingof the turbofan, determining a vibratory response of the turbofan basedon the acceleration data, determining a second severity level parameterbased on the vibratory response and a weight value, and detecting inletflow separation at an inlet of turbofan based on the first severitylevel parameter and the second severity level parameter.

27. The method of any preceding clause wherein the first pressure sensoris coupled to an outer lip of the nacelle, the second pressure sensor iscoupled to an inner lip of the nacelle, and further including obtainingaltitude data and speed data from an aircraft coupled to the turbofan,determining an air density based on the altitude data, determining aMach number based on the speed data, and determining the inlet flowseparation parameter based on at least one of the first pressure value,the second pressure value, the air density, or the Mach number.

28. The method of any preceding clause wherein adjusting thecontribution of airflow from aft of the fan includes controlling anactuator included in the nacelle based on the severity level parameter,the actuator to move from a first position to a second position toadjust the contribution of the airflow from aft of the fan to forward ofthe fan.

29. An apparatus comprising hardware, and memory including instructionsthat, when executed, cause the hardware to at least determine an inletflow separation parameter based on a first pressure value from a firstpressure sensor included in a nacelle of a turbofan and a secondpressure value from a second pressure sensor included in the nacelle,and determine a severity level parameter based on the inlet flowseparation parameter, the severity level parameter based on a differencebetween the first pressure value and the second pressure value.

30. The apparatus of any preceding clause wherein the hardware is toadjust a contribution of airflow from aft of a fan of the turbofan basedon the severity level parameter.

31. The apparatus of any preceding clause the first pressure sensor iscoupled to an outer lip of the nacelle, the severity level parameter isa first severity level parameter, and the hardware to determine anairflow direction at the outer lip based on a difference between thefirst pressure value and a threshold, determine a second severity levelparameter based on the difference and a weight value, and detect inletflow separation at an inlet of turbofan based on the first severitylevel parameter and the second severity level parameter.

32. The apparatus of any preceding clause wherein the hardware is todetermine a first probability density function based on the firstseverity level parameter and the second severity level parameter,compare the first probability density function to a second probabilitydensity function stored in a database, and detect the inlet flowseparation at the inlet of the turbofan based on the comparison.

33. The apparatus of any preceding clause wherein the first pressuresensor is coupled to an outer lip of the nacelle, the second pressuresensor is coupled to an inner lip of the nacelle, the severity levelparameter corresponding to a nacelle inlet pressure difference, and thehardware to determine the nacelle inlet pressure difference based on adifference between the first pressure value and the second pressurevalue, determine the severity level parameter based on the nacelle inletpressure difference and a weight value, and detect inlet flow separationat an inlet of turbofan based on the severity level parameter.

34. The apparatus of any preceding clause wherein the severity levelparameter is a first severity level parameter, and the hardware toobtain acceleration data from an accelerometer coupled to a bearing ofthe turbofan, determine a vibratory response of the turbofan based onthe acceleration data, determine a second severity level parameter basedon the vibratory response and a weight value, and detect inlet flowseparation at an inlet of turbofan based on the first severity levelparameter and the second severity level parameter.

35. The apparatus of any preceding clause wherein the first pressuresensor is coupled to an outer lip of the nacelle, the second pressuresensor is coupled to an inner lip of the nacelle, and the hardware toobtain altitude data and speed data from an aircraft coupled to theturbofan, determine an air density based on the altitude data, determinea Mach number based on the speed data, and determine the inlet flowseparation parameter based on at least one of the first pressure value,the second pressure value, the air density, or the Mach number.

36. The apparatus of any preceding clause wherein the hardware is toadjust a contribution of airflow from aft of the fan by controlling anactuator included in the nacelle based on the severity level parameter,the actuator to move from a first position to a second position toadjust the contribution of the airflow from aft of the fan to forward ofthe fan.

Although certain example methods, apparatus and articles of manufacturehave been disclosed herein, the scope of coverage of this patent is notlimited thereto. On the contrary, this patent covers all methods,apparatus and articles of manufacture fairly falling within the scope ofthe claims of this patent.

The following claims are hereby incorporated into this DetailedDescription by this reference, with each claim standing on its own as aseparate embodiment of the present disclosure.

1. An apparatus comprising: hardware; and memory including instructionsthat, when executed, cause the hardware to at least: determine an inletflow separation parameter based on a first pressure value from a firstpressure sensor included in a nacelle of a turbofan and a secondpressure value from a second pressure sensor included in the nacelle;determine a severity level parameter based on the inlet flow separationparameter, the severity level parameter based on a difference betweenthe first pressure value and the second pressure value; and adjust acontribution of airflow from aft of a fan of the turbofan based on theseverity level parameter.
 2. The apparatus of claim 1, wherein the firstpressure sensor is coupled to an outer lip of the nacelle, the severitylevel parameter is a first severity level parameter, and the hardwareto: determine an airflow direction at the outer lip based on adifference between the first pressure value and a threshold; determine asecond severity level parameter based on the difference and a weightvalue; and detect inlet flow separation at an inlet of turbofan based onthe first severity level parameter and the second severity levelparameter.
 3. The apparatus of claim 2, wherein the hardware is to:determine a first probability density function based on the firstseverity level parameter and the second severity level parameter;compare the first probability density function to a second probabilitydensity function stored in a database; and detect the inlet flowseparation at the inlet of the turbofan based on the comparison.
 4. Theapparatus of claim 1, wherein the first pressure sensor is coupled to anouter lip of the nacelle, the second pressure sensor is coupled to aninner lip of the nacelle, the severity level parameter corresponding toa nacelle inlet pressure difference, and the hardware to: determine thenacelle inlet pressure difference based on a difference between thefirst pressure value and the second pressure value; determine theseverity level parameter based on the nacelle inlet pressure differenceand a weight value; and detect inlet flow separation at an inlet ofturbofan based on the severity level parameter.
 5. The apparatus ofclaim 1, wherein the severity level parameter is a first severity levelparameter, and the hardware to: obtain acceleration data from anaccelerometer coupled to a bearing of the turbofan; determine avibratory response of the turbofan based on the acceleration data;determine a second severity level parameter based on the vibratoryresponse and a weight value; and detect inlet flow separation at aninlet of turbofan based on the first severity level parameter and thesecond severity level parameter.
 6. The apparatus of claim 1, whereinthe first pressure sensor is coupled to an outer lip of the nacelle, thesecond pressure sensor is coupled to an inner lip of the nacelle, andthe hardware to: obtain altitude data and speed data from an aircraftcoupled to the turbofan; determine an air density based on the altitudedata; determine a Mach number based on the speed data; and determine theinlet flow separation parameter based on at least one of the firstpressure value, the second pressure value, the air density, or the Machnumber.
 7. The apparatus of claim 1, wherein the hardware is to adjustthe contribution of airflow from aft of the fan by controlling anactuator included in the nacelle based on the severity level parameter,the actuator to move from a first position to a second position toadjust the contribution of the airflow from aft of the fan to forward ofthe fan.
 8. An apparatus comprising: an inlet flow separation parameterdeterminer to determine an inlet flow separation parameter based on afirst pressure value from a first pressure sensor included in a nacelleof a turbofan and a second pressure value from a second pressure sensorincluded in the nacelle; an inlet flow separation severity levelparameter determiner to determine a severity level parameter based onthe inlet flow separation parameter, the severity level parameter basedon a difference between the first pressure value and the second pressurevalue; and a command generator to adjust a contribution of airflow fromaft of a fan of the turbofan based on the severity level parameter. 9.The apparatus of claim 8, wherein the first pressure sensor is coupledto an outer lip of the nacelle, the severity level parameter is a firstseverity level parameter, the inlet flow separation severity levelparameter determiner to: determine an airflow direction at the outer lipbased on a difference between the first pressure value and a threshold;and determine a second severity level parameter based on the differenceand a weight value; and further including an inlet flow separationdetector to detect inlet flow separation at an inlet of turbofan basedon the first severity level parameter and the second severity levelparameter.
 10. The apparatus of claim 9, wherein the inlet flowseparation detector is to: determine a first probability densityfunction based on the first severity level parameter and the secondseverity level parameter; compare the first probability density functionto a second probability density function stored in a database; anddetect the inlet flow separation at the inlet of the turbofan based onthe comparison.
 11. The apparatus of claim 8, wherein the first pressuresensor is coupled to an outer lip of the nacelle, the second pressuresensor is coupled to an inner lip of the nacelle, the severity levelparameter corresponding to a nacelle inlet pressure difference, theinlet flow separation severity level parameter determiner to: determinethe nacelle inlet pressure difference based on a difference between thefirst pressure value and the second pressure value; determine theseverity level parameter based on the nacelle inlet pressure differenceand a weight value; and further including an inlet flow separationdetector to detect inlet flow separation at an inlet of turbofan basedon the severity level parameter.
 12. The apparatus of claim 8, whereinthe severity level parameter is a first severity level parameter,further including a collection engine to obtain acceleration data froman accelerometer coupled to a bearing of the turbofan, the inlet flowseparation severity level parameter determiner is to: determine avibratory response of the turbofan based on the acceleration data;determine a second severity level parameter based on the vibratoryresponse and a weight value; and further including an inlet flowseparation detector to detect inlet flow separation at an inlet ofturbofan based on the first severity level parameter and the secondseverity level parameter.
 13. The apparatus of claim 8, wherein thefirst pressure sensor is coupled to an outer lip of the nacelle, thesecond pressure sensor is coupled to an inner lip of the nacelle, andfurther including a collection engine to obtain altitude data and speeddata from an aircraft coupled to the turbofan, and the inlet flowseparation parameter determiner to: determine an air density based onthe altitude data; determine a Mach number based on the speed data; anddetermine the inlet flow separation parameter based on at least one ofthe first pressure value, the second pressure value, the air density, orthe Mach number.
 14. The apparatus of claim 8, wherein the commandgenerator is to adjust the contribution of airflow from aft of the fanby controlling an actuator included in the nacelle based on the severitylevel parameter, the command generator to invoke the actuator to movefrom a first position to a second position to adjust the contribution ofthe airflow from aft of the fan to forward of the fan.
 15. Anon-transitory computer readable storage medium comprising instructionsthat, when executed, cause at least one processor to at least: determinean inlet flow separation parameter based on a first pressure value froma first pressure sensor included in a nacelle of a turbofan and a secondpressure value from a second pressure sensor included in the nacelle;determine a severity level parameter based on the inlet flow separationparameter, the severity level parameter based on a difference betweenthe first pressure value and the second pressure value; and adjust acontribution of airflow from aft of a fan of the turbofan based on theseverity level parameter.
 16. The non-transitory computer readablestorage medium of claim 15, wherein the first pressure sensor is coupledto an outer lip of the nacelle, the severity level parameter is a firstseverity level parameter, and the instructions, when executed, cause theat least one processor to: determine an airflow direction at the outerlip based on a difference between the first pressure value and athreshold; determine a second severity level parameter based on thedifference and a weight value; and detect inlet flow separation at aninlet of turbofan based on the first severity level parameter and thesecond severity level parameter.
 17. The non-transitory computerreadable storage medium of claim 16, wherein the instructions, whenexecuted, cause the at least one processor to: determine a firstprobability density function based on the first severity level parameterand the second severity level parameter; compare the first probabilitydensity function to a second probability density function stored in adatabase; and detect the inlet flow separation at the inlet of theturbofan based on the comparison.
 18. The non-transitory computerreadable storage medium of claim 15, wherein the first pressure sensoris coupled to an outer lip of the nacelle, the second pressure sensor iscoupled to an inner lip of the nacelle, the severity level parametercorresponding to a nacelle inlet pressure difference, and theinstructions, when executed, cause the at least one processor to:determine the nacelle inlet pressure difference based on a differencebetween the first pressure value and the second pressure value;determine the severity level parameter based on the nacelle inletpressure difference and a weight value; and detect inlet flow separationat an inlet of turbofan based on the severity level parameter.
 19. Thenon-transitory computer readable storage medium of claim 15, wherein theseverity level parameter is a first severity level parameter, and theinstructions, when executed, cause the at least one processor to: obtainacceleration data from an accelerometer coupled to a bearing of theturbofan; determine a vibratory response of the turbofan based on theacceleration data; determine a second severity level parameter based onthe vibratory response and a weight value; and detect inlet flowseparation at an inlet of turbofan based on the first severity levelparameter and the second severity level parameter.
 20. Thenon-transitory computer readable storage medium of claim 15, wherein thefirst pressure sensor is coupled to an outer lip of the nacelle, thesecond pressure sensor is coupled to an inner lip of the nacelle, andthe instructions, when executed, cause the at least one processor to:obtain altitude data and speed data from an aircraft coupled to theturbofan; determine an air density based on the altitude data; determinea Mach number based on the speed data; and determine the inlet flowseparation parameter based on at least one of the first pressure value,the second pressure value, the air density, or the Mach number.
 21. Thenon-transitory computer readable storage medium of claim 15, wherein theinstructions, when executed, cause the at least one processor to adjustthe contribution of airflow from aft of the fan by controlling anactuator included in the nacelle based on the severity level parameter,the actuator to move from a first position to a second position toadjust the contribution of the airflow from aft of the fan to forward ofthe fan. 22-36. (canceled)